Soft metal and method for preparation thereof, and exterior part of watch and method for preparation thereof

ABSTRACT

A soft metal and a decorative article of wristwatch are produced by forming, on the surface of a soft metal article ( 2 ), a hard layer ( 3, 13 ) containing zirconium and molybdenum, or containing zirconium, molybdenum and further an additive element constituted of at least one or more elements selected from niobium, tantalum, and titanium. It is preferable that the content of molybdenum constituting the hard layer ( 3, 13 ) is about 30 to 75 wt %, or that the content of molybdenum is about 25 to 65 wt % and the total content of the additive elements is about 25 wt % or less.

TECHNICAL FIELD

[0001] The present invention relates to a soft metal that comprises stainless steel, iron base alloy, titanium, titanium alloy, aluminum, aluminum alloy, brass, copper, copper alloy, magnesium, magnesium alloy or the like and has high abrasion resistance, high corrosion resistance, and strength and a method of producing the same, and a decorative article of wristwatch that is strong, resistant to corrosion, and excellent in durability and provides a high-class feeling to the external appearance and a method of producing the same.

BACKGROUND TECHNOLOGY

[0002] Since soft metals including stainless steel, iron base alloy, titanium, titanium alloy, aluminum, aluminum alloy, brass, copper, copper alloy, magnesium, and magnesium alloy are light in weight and inexpensive, these metals are worked into a wide variety of components for use in various fields. Examples of a soft metal article formed by processing the soft metals include decorative articles of wristwatch, such as a wristwatch case, wristwatch bezel, wristwatch case back, wristwatch band, clasp, crown, and so forth.

[0003] Meanwhile, the soft metals are inferior in terms of abrasion resistance because the surface hardness thereof is as low as not more than Hv=200 of Vickers hardness, thereby rendering the surface thereof susceptible to scratches. Further, softer metals such as iron base alloy, except stainless steel, titanium, and titanium alloy, aluminum, aluminum alloy, brass, copper, copper alloy, magnesium, magnesium alloy and so forth, have a property susceptible to corrosion because of their poor corrosion resistance. Accordingly, with the aim of improving the abrasion resistance and corrosion resistance of the soft metals used as the constituent material of soft metal articles, attempts have so far been made to apply various surface hardening treatments for hardening the surface of the soft metal articles to the surface thereof.

[0004] As methods of hardening the surface of the soft metal, there are generally available a method of forming a film coating the surface thereof, and a method of hardening the soft metal itself.

[0005] Examples of the method of forming a film on the surface of the soft metal include processes such as wet electroplating, ion plating, and so forth. As the wet electroplating, there are in widespread use nickel electroplating, nickel-phosphorus alloy electroplating, nickel-palladium alloy electroplating and so forth, however, an electroplating film formed by any of the processes described is soft and has not reached such a condition as to eliminate the risk of scratches being caused by impacts.

[0006] On the other hand, as the ion plating, there are cited processes of forming a film such as a hard carbon film, titanium nitride film, and so froth. However, since it is difficult to directly coat the soft metal, such as aluminum, aluminum alloy, brass, copper, copper alloy and so forth, with the hard carbon film, there is the need for forming the hard carbon film with an intermediate layer made of silicon, germanium, titanium and so forth, interposed therebetween. As a result, there exist more interfaces in this case due to the presence of the intermediate layer than in the case of directly coating the soft metal, resulting in a tendency that the hard carbon film is prone to peeling to that extent. Further, the titanium nitride film has poor adhesion property against the soft metal due to its high internal stress, so that the titanium nitride film has a property to be prone to peeling. Thus, with the ion plating, there has not been completely solved a problem that, whichever film is formed, the film is prone to peeling. Furthermore, there exists another problem that once the film, which is so important, is peeled, part of the soft metal itself is exposed, so that initiation of corrosion starts from that part, thereby rendering the soft metal unfit for use in the soft metal article.

[0007] As methods of directly hardening the soft metal itself, there have been known ion implantation, ion nitriding, gas nitriding, carburizing, and so forth. However, with any of those methods, since many hours are required in application of a hardening treatment, a soft metal article cannot be efficiently produced. In addition, with the use of any of those methods, grain coarsening of the soft metal results because of high temperature needed for the hardening treatment, thereby involving the risk of occurrence of surface roughness. For example, upon application of a gas nitriding to a soft metal article after applying a mirror surface polishing thereto, there occurs surface roughness of 200 to 300 μm due to the grain coarsening of the soft metal article after the gas nitriding, thereby causing a mirror surface to disappear, whereupon it becomes impossible to restore a mirror surface condition which has existed prior to the application of the gas nitriding even if a polishing is applied thereto thereafter, so that quality will be considerably impaired in terms of decorativeness of the external appearance. Especially for decorative articles of wristwatch, in particular, for decorative articles of wristwatch such as a wristwatch case, wristwatch bezel, wristwatch case back, and so forth, the quality in terms of decorativeness of the external appearance is an important element, and therefore deterioration in the quality in terms of decorativeness of the external appearance is a serious problem.

[0008] On the other hand, there is a case where those decorative articles of wristwatch are produced of an insulating material such as resin, ceramics, or the like besides the typical soft metals, and it is needless to say that the quality in terms of decorativeness of the external appearance is important also in this case so long as they are decorative articles of wristwatch. Accordingly, it is important that the surface of even decorative article of wristwatch produced of an insulating material is rendered insusceptible to scratches by enhancing abrasion resistance and is improved in the quality of decorativeness in terms of the external appearance by improving corrosion resistance so as to provide a high-class feeling to the external appearance of, especially a wristwatch, to be produced.

[0009] The invention has been developed to solve the problems described above, and it is an object of the invention to provide a soft metal and a method of producing the same, and a decorative article of wristwatch and a method of producing the same, wherein the surface thereof is rendered insusceptible to scratches by enhancing abrasion resistance and initiation of corrosion is prevented by improving corrosion resistance so as to provide excellent durability and a high-class feeling to the external appearance.

DISCLOSURE OF THE INVENTION

[0010] A soft metal according to the invention is characterized in that a hard layer containing zirconium and molybdenum is formed on a surface thereof. This hard layer either in the crystal phase and amorphous phase is high in Vickers hardness and mechanical strength. Further, the hard layer has a property of initiating no corrosion even if it is brought into contact with a substance exhibiting acidity or alkalinity by immersion therein for a long time.

[0011] Further, in the soft metal, the hard layer may contain an additive element comprising at least one or more elements selected from niobium, tantalum, and titanium.

[0012] Furthermore, the hard layer is preferably formed through an intermediate hard layer made of an alloy constituted of at least one selected from iron, cobalt, and nickel. In this case, the soft metal is further increased in hardness of the surface, improved in abrasion resistance, and rendered insusceptible to scratches on the surface.

[0013] In this soft metal, it is suitable that a content of molybdenum constituting the hard layer is about 30 to 75 wt %. When the hard layer contains the additive elements, it is preferable that a content of molybdenum constituting the hard layer is about 25 to 65 wt %, and a total content of the additive elements is about 25 wt % or less. Besides, when the hard layer contains the additive elements, it is also adoptable that a total content of molybdenum and additive elements constituting the hard layer is about 30 wt % or more and about 80 wt % or less. When these conditions are satisfied, the hard layer is high in abrasion resistance and corrosion resistance to provide a more preferable soft metal that is the object of the invention.

[0014] Further, in the soft metal, it is preferable that a content of molybdenum constituting the hard layer is about 30 to 60 wt %, and when the hard layer contains the additive elements, it is also preferable that a total content of molybdenum and additive elements constituting the hard layer is about 30 to 55 wt %. In this case, the hard layer is in the amorphous phase, so that the surface of the soft metal becomes a mirror surface, resulting in a smooth film similar to the film formed by the CVD method.

[0015] Further, the invention provides a method of producing a soft metal, comprising steps of: disposing a soft metal and an alloy target containing zirconium and molybdenum inside a vacuum apparatus; evacuating the vacuum apparatus and then introducing an inert gas thereinto and causing an inert gas plasma to occur; and forming a hard layer made of metals constituting the alloy target on a surface of the soft metal in an inert gas plasma atmosphere in which the inert gas plasma is caused to occur.

[0016] Further, the invention provides a method of producing a soft metal, comprising steps of: disposing a soft metal and a first alloy target containing at least one selected from iron, cobalt, and nickel inside a vacuum apparatus; evacuating the vacuum apparatus, then introducing an inert gas thereinto and causing an inert gas plasma to occur; forming an intermediate hard layer made of metals constituting the first alloy target on a surface of the soft metal in an inert gas plasma atmosphere in which the inert gas plasma is caused to occur; and subsequently disposing a second alloy target containing zirconium and molybdenum inside the vacuum apparatus, causing an inert gas plasma to occur, and forming a hard layer made of metals constituting the second alloy target on a surface of the intermediate hard layer in an atmosphere of the inert gas plasma.

[0017] In these methods of producing a soft metal, it is possible that the alloy target or the second alloy target contains an additive element constituted of at least one or more elements selected from niobium, tantalum, and titanium.

[0018] Besides, the invention provides a decorative article of wristwatch wherein a hard layer containing zirconium and molybdenum is formed on a surface of a metal decorative base material made of a soft metal.

[0019] In the decorative article of wristwatch, the hard layer may contain an additive element constituted of at least one or more elements selected from niobium, tantalum, and titanium.

[0020] Further, it is preferable that the hard layer is formed through an intermediate hard layer made of an alloy containing at least one selected from iron, cobalt, and nickel.

[0021] Further, in the decorative article of wristwatch, it is suitable that a content of molybdenum constituting the hard layer is about 30 to 75 wt %. When the hard layer contains the additive elements, it is preferable that a content of molybdenum constituting the hard layer is about 25 to 65 wt %, and a total content of the additive elements is about 25 wt % or less. Further, when the hard layer contains the additive elements, it is also adoptable that a total content of molybdenum and additive elements constituting the hard layer is about 30 to 80 wt %.

[0022] In the decorative article of wristwatch, it is suitable that a content of molybdenum constituting the hard layer is about 30 to 60 wt %, and when the hard layer contains the additive elements, it is preferable that a total content of molybdenum and additive elements constituting the hard layer is about 30 to 55 wt %.

[0023] Further, the invention provides a decorative article of wristwatch wherein a hard layer containing zirconium and molybdenum is formed on a surface of an insulating decorative base material made of an insulator.

[0024] In the decorative article of wristwatch, the hard layer may contain an additive element constituted of at least one or more elements selected from niobium, tantalum, and titanium.

[0025] It is preferable that the hard layer is formed through an intermediate layer made of resin.

[0026] Further, it is more preferable that a protective film made of a transparent resin is formed on a surface of the hard layer.

[0027] Further, in the decorative article of wristwatch, it is suitable that a content of molybdenum constituting the hard layer is about 30 to 75 wt %. When the hard layer contains additive elements, it is preferable that a content of molybdenum constituting the hard layer is about 25 to 65 wt %, and a total content of the additive elements is about 25 wt % or less.

[0028] Further, in the decorative article of wristwatch, it is suitable that a content of molybdenum constituting the hard layer is about 30 to 60 wt %. When the hard layer contains additive elements, it is preferable that a total content of molybdenum and additive elements constituting the hard layer is about 30 to 55 wt %.

[0029] The insulating decorative base material is preferably made of resin or ceramics.

[0030] Besides, it is suitable that the hard layer is a metal film formed by sputtering.

[0031] Furthermore, the invention provides a method of producing a decorative article of wristwatch, comprising steps of: disposing a metal decorative base material made of a soft metal and an alloy target containing zirconium and molybdenum inside a vacuum apparatus; evacuating the vacuum apparatus, then introducing an inert gas thereinto and causing an inert gas plasma to occur; and forming a hard layer made of metals constituting the alloy target on a surface of the metal decorative base material in an inert gas plasma atmosphere in which the inert gas plasma is caused to occur.

[0032] Further, a method of producing a decorative article of wristwatch when the intermediate hard layer is formed, comprises steps of: disposing a metal decorative base material made of a soft metal and a first alloy target containing at least one selected from iron, cobalt, and nickel inside a vacuum apparatus; evacuating the vacuum apparatus, then introducing an inert gas thereinto and causing an inert gas plasma to occur; forming an intermediate hard layer made of metals constituting the first alloy target on a surface of the metal decorative base material in an inert gas plasma atmosphere in which the inert gas plasma is caused to occur; and subsequently disposing a second alloy target containing zirconium and molybdenum inside the vacuum apparatus, causing an inert gas plasma to occur, and forming a hard layer made of metals constituting the second alloy target on a surface of the intermediate hard layer in an atmosphere of the inert gas plasma.

[0033] Furthermore, the invention provides a method of producing a decorative article of wristwatch, comprising steps of: disposing an insulating decorative base material made of an insulator and an alloy target containing zirconium and molybdenum inside a vacuum apparatus; evacuating the vacuum apparatus, then introducing an inert gas thereinto and causing an inert gas plasma to occur; and causing atoms of metals constituting the alloy target to adhere to a surface of the insulating decorative base material in an inert gas plasma atmosphere in which the inert gas plasma is caused to occur, to thereby form a hard layer composed of the atoms of the metals on the surface of the insulating decorative base material.

[0034] In these methods of producing a decorative article of wristwatch, it is possible that the alloy target or the second alloy target contains an additive element constituted of at least one or more elements selected from niobium, tantalum, and titanium.

BRIEF DESCRIPTION OF DRAWINGS

[0035]FIG. 1 and FIG. 2 are enlarged schematic sectional views each showing the principal part of a soft metal according to the invention;

[0036]FIG. 3 and FIG. 4 are schematic sectional views each showing a decorative article of wristwatch and an enlarged principal part thereof;

[0037]FIG. 5 and FIG. 6 are schematic sectional views each showing the configuration in a vacuum apparatus in which a hard layer is formed on the surface of a soft metal or a decorative article of wristwatch;

[0038]FIG. 7 and FIG. 8 are enlarged schematic sectional views each showing the principal part of a soft metal having a hard layer formed thereon through an intermediate hard layer;

[0039]FIG. 9 and FIG. 10 are schematic sectional views each showing a decorative article of wristwatch having a hard layer formed thereon through an intermediate hard layer and an enlarged principal part thereof;

[0040]FIG. 11 is and FIG. 12 are schematic sectional views each showing the configuration in a vacuum apparatus in which a hard layer is formed on the surface of a soft metal or a decorative article of wristwatch through an intermediate hard layer;

[0041]FIG. 13 is a schematic sectional view showing a flat plate-shaped soft metal article and an enlarged principal part thereof, a part (1) showing a soft metal article having a hard layer 3 formed thereon and a part (2) showing a soft metal article having a hard layer 13 formed thereon;

[0042]FIG. 14 is a schematic sectional view showing another flat plate-shaped soft metal article and an enlarged principal part thereof, a part (1) showing a soft metal article having a hard layer 3 formed thereon and a part (2) showing a soft metal article having a hard layer 13 formed thereon;

[0043]FIG. 15 is a schematic sectional view showing a wristwatch case using an insulating decorative base material and an enlarged principal part thereof;

[0044]FIG. 16 is a schematic sectional view showing a case back using an insulating decorative base material and an enlarged principal part thereof;

[0045]FIG. 17 is a schematic sectional view showing another wristwatch case using an insulating decorative base material and an enlarged principal part thereof;

[0046]FIG. 18 is a schematic sectional view showing another case back using an insulating decorative base material and an enlarged principal part thereof;

[0047]FIG. 19 is a schematic sectional view showing still another wristwatch case using an insulating decorative base material and an enlarged principal part thereof;

[0048]FIG. 20 is a schematic sectional view showing still another case back using an insulating decorative base material and an enlarged principal part thereof; and

[0049]FIG. 21 is a schematic sectional view showing the internal structure of a radio controlled wristwatch using a wristwatch case and a wristwatch case back being examples of the decorative article of wristwatch according to the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0050] Preferred embodiments of a soft metal and a method of producing the same, and a decorative article of wristwatch and a method of producing the same, according to the invention, are described in detail hereinafter with reference to the accompanying drawings.

First Embodiment

[0051] 1) A Structure of a Soft Metal and a Method of Producing the Same

[0052]FIG. 1 is an enlarged schematic sectional view showing the principal part of a soft metal 1 according to the invention, and FIG. 2 is a similar enlarged schematic sectional view showing the principal part of a soft metal 15. The soft metal 1 is composed of a soft metal portion 2 and a hard layer 3 containing zirconium (Zr) and molybdenum (Mo) formed on the surface of the soft metal portion 2. The soft metal 15 is composed of a soft metal portion 2 and a hard layer 13 formed on the surface of the soft metal portion 2, wherein the hard layer 13 contains Zr and Mo and further an additive element comprising at least one or more elements having homogeneous solubility with Zr and Mo, that is, selected from niobium (Nb), tantalum (Ta), and titanium (Ti). It should be noted that both of the hard layer 3 and the hard layer 13 are thin in thickness in comparison with the soft metal portions 2, omitting therefore the hard layer 3 and the hard layer 13 on both the right and left sides as well as the underside of the soft metal portions 2 in FIG. 1 and FIG. 2.

[0053] The hard layer 3 and the hard layer 13 in both crystal phase and amorphous phase are high in Vickers hardness and mechanical strength. Further, the hard layer 3 and the hard layer 13 have a property of initiating no corrosion even if they are in contact with a substance exhibiting acidity or alkalinity by immersion therein for a long time. Therefore, the soft metal 1 and the soft metal 15 are excellent in abrasion resistance and corrosion resistance owing to the hard layer 3 and the hard layer 13 formed thereon, respectively.

[0054] Next, structures of the soft metal 1 and the soft metal 15, methods of producing the same, and effects of the same are described in detail. It should be noted that the soft metal 1 and the soft metal 15 are different only in composition of the hard layer formed on the surface and are the same in the other structure and method of producing the same, and therefore they are described by taking an example of a soft metal article 5 described hereinafter.

[0055] The soft metal article 5 is produced by using a soft metal article 6 obtained by working a soft metal, such as stainless steel, iron base alloy, titanium, titanium alloy, aluminum, aluminum alloy, brass, copper, copper alloy, magnesium, or magnesium alloy, into desired shapes of various components, and by forming the hard layer 3 or the hard layer 13 on the surface of the soft metal article 6. The soft metal article 5 having the hard layer 3 formed thereon corresponds to the soft metal 1, and the soft metal article 5 having the hard layer 13 formed thereon corresponds to the soft metal 15.

[0056] The soft metal article 5 is produced in the following manner.

[0057] As shown in FIG. 5, the soft metal article 6 and an alloy target 4 are first disposed inside a vacuum apparatus 100. As the alloy target 4, an alloy containing Zr and Mo (hereinafter referred to as a “Zr—Mo alloy”) and an alloy containing Zr and Mo and the above-described additive element (hereinafter referred to as a “Zr—Mo additive element alloy”) are prepared. The former is used to form the hard layer 3, and the latter is used to form the hard layer 13. Subsequently, the vacuum apparatus 100 is evacuated through a pump 101, and thereafter, an inert gas (for example, an argon (Ar) gas) is introduced therein, an internal pressure is maintained in the order of 3 ×10⁻³ Torr (about 0.4 Pa), and an inert gas plasma is caused to occur. In such an inert gas plasma atmosphere, a film made of metals constituting the alloy target 4 is formed on the surface of the soft metal article 6 by a sputter method (also called a sputtering method), resulting in the soft metal article 5. Here, the use of the Zr—Mo alloy for the alloy target 4 results in the soft metal article 5 having the hard layer 3 formed on the surface thereof, and the use of the Zr—Mo additive element alloy results in the soft metal article 5 having the hard layer 13 formed on the surface thereof.

[0058] 2) A Structure of a Decorative Article of Wristwatch and a Method of Producing the Same

[0059] Next, a structure of a decorative article of wristwatch and a method of producing the same are described. FIG. 3 is a schematic sectional view showing a wristwatch case 16 being an example of a decorative article of wristwatch according to the invention and an enlarged principal part thereof, and FIG. 4 is a similar schematic sectional view showing a wristwatch case 26 and an enlarged principal part thereof. The wristwatch case 16 has the above-described hard layer 3 formed on the surface of a metal decorative base material 12 made of a soft metal, and the wristwatch case 26 has the hard layer 13 formed on the surface of a metal decorative base material 12.

[0060] The wristwatch cases 16 and 26 are high and excellent in abrasion resistance and corrosion resistance, similarly to the soft metals 1 and 15, owing to the hard layer 3 and the hard layer 13 formed thereon, respectively. Accordingly, the wristwatch cases 16 and 26 are rendered insusceptible to scratches on the surface and have high quality in terms of decorativeness of the external appearance, and thus can provide a high-class feeling to the external appearance when used especially for a wristwatch.

[0061] The wristwatch cases 16 and 26 are produced using the metal decorative base material 12 having a shape of a wristwatch case in the same method as that of the soft metal article 5. More specifically, as shown in FIG. 6, the metal decorative base material 12 and an alloy target 4 are disposed inside a vacuum apparatus 100. As the alloy target 4, a Zr—Mo alloy target and a Zr—Mo additive element alloy target are prepared respectively. Subsequently, the vacuum apparatus 100 is evacuated through a pump 101, thereafter, an inert gas is introduced therein and an internal pressure is maintained in the order of, for example, 3×10⁻³ Torr (about 0.4 Pa), and an inert gas plasma is caused to occur. In such an inert gas plasma atmosphere, a film made of metals constituting the alloy target 4 is formed on the surface of the metal decorative base material 12 by a sputter method, thereby forming the wristwatch case 16 or 26. Here, the use of the Zr—Mo alloy for the alloy target 4 results in the wristwatch case 16, and the use of the Zr—Mo additive element alloy results in the wristwatch case 26.

[0062] 3) First Examples of the Soft Metal and the Decorative Article of Wristwatch

[0063] Concrete examples (samples) of the above-described soft metal and decorative article of wristwatch were produced. Those examples are described with reference to Table 1 to Table 3. The soft metal articles 5 were produced here according to the above-described procedure using a flat plate-shaped soft metal article as shown in FIG. 13. In this event, for the soft metal as the material, five kinds of metals in total were used, that is, two kinds of stainless steels (SUS316L and SUS304), titanium (Ti), brass, and aluminum (Al). As the alloy target 4, several kinds of Zr—Mo alloys and Zr—Mo additive element alloys were prepared respectively by appropriately changing the composition of the respective metals.

[0064] As the decorative articles of wristwatch, in addition to the above-described wristwatch cases 16 and 26, several kinds of wristwatch bezels, (hereinafter referred to as “bezels”), wristwatch bands, wristwatch case backs (hereinafter referred to as “case backs”), and clasps were prepared using appropriate soft metals from among those similar to the soft metal articles 5. As the alloy target 4, several kinds of Zr—Mo alloys and Zr—Mo additive element alloys were prepared respectively by appropriately changing the composition of the respective metals.

[0065] Further, samples (comparative examples) for comparison with the examples of the soft metal articles 5 thus produced were also prepared. The comparative examples are formed using stainless steel (SUS316L) and titanium (Ti) with a Ni—P electroplating film formed on the surface thereof by a wet electroplating process. Further, comparative examples (comparative examples 5 to 20) for obtaining more preferable soft metals and decorative articles of wristwatch that are the object of the invention were also produced.

[0066] With each of the produced examples and comparative examples of the soft metal articles 5 and decorative articles of wristwatch, the film formed thereon was subjected to the ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectroscopy), whereby the alloying composition thereof was checked. The result of this is presented as a “composition of a hard layer.” Besides, as the items for evaluating the characteristics of the film (hereinafter these items being referred to as “evaluation items”), four items of “hardness,” “surface roughness,” “adhesion property,” and “corrosion resistance” were selected, and reference values were set for the respective items so that conditions were examined for obtaining a more preferable soft metal and decorative article of wristwatch that are the object of the invention. The evaluation was made on the respective items according to the following procedure.

[0067] The “hardness” of the surface of the film was measured with a Vickers hardness tester, and the film having a Vickers hardness under the condition of a load of 50 gf of Hv=600 or more was determined as acceptable. As for the “surface roughness,” the average surface roughness Ra was measured with a surface roughness gauge, and the film having an Ra of 0.4 μm or less was determined as acceptable. As for the. “adhesion property,” a scratch test by scratching the surface of the film was conducted to measure a peeling starting load, and the film having a peeling starting load of 500 gf or more was determined as acceptable. As for the corrosion resistance, the film in which no corrosion occurred at all after immersion of the film in a CASS testing (Copper Accelerated Acetic Acid Salt Splay testing) solution for 48 hours was determined as acceptable. Then, the film evaluated as acceptable on all the four items “hardness,” “surface roughness,” “adhesion property,” and “corrosion resistance” was determined as acceptable in overall evaluation, and the film evaluated as unacceptable on one of them was determined as unacceptable in overall evaluation. The evaluation results are as follows.

[0068] A) The Case of Using a Zr—Mo Alloy

[0069] This case is shown in Table 1 and Table 3. As shown in Table 1, comparative examples 1 to 4 are “no” for the corrosion resistance. However, the hardness is Hv=360 (comparative example 3) even at maximum, the surface roughness Ra is 0.1 μm, and the adhesion property is no more than 350 gf (comparative example 3) even at maximum, and therefore these examples are unacceptable in overall evaluation.

[0070] In contrast to the above, each of the examples, as shown in examples 1 to 12 in Table 1 and examples 51 to 56 in Table 3, has a hardness Hv=620 or more. Further, the average surface roughness Ra is 0.35 μm or less, and the peeling starting load is 500 gf or more. All the examples have “no” corrosion. Accordingly, the examples 1 to 12 shown in Table 1 and the examples 51 to 56 shown in Table 3 (hereinafter referred to as “first objective examples”) are acceptable in overall evaluation.

[0071] In addition to the first objective examples, as shown in comparative examples 5 to 10, the hard layer 3 increases in hardness with an increase in Mo content. In consideration of this point, the first objective examples are compared with the comparative examples 5 to 10 shown in Table 3, reaching the following understanding.

[0072] In terms of the increase in hardness with an increase in the Mo content, it is only required to increase the Mo content in order to make the film higher in hardness. However, as shown in the comparative examples 5 to 7, when the Mo content reaches 76 wt %, that is, more than 75 wt %, the average surface roughness Ra becomes 0.45 μm. In this event, a hard layer is formed, in which crystalline Mo₂Zr is formed and the crystal grain boundary bulges up, presenting a lot of surface roughness. Therefore, that hard layer might affect the decorativeness of the external appearance of the soft metal and decorative article of wristwatch. Within a range of the Mo content of 75 wt % or less and more than 60 wt %, Mo₂Zr is formed in the hard layer but the crystal grain boundary does not coarsen, presenting little or no surface roughness. Accordingly, the Mo content is acceptably less than 76 wt % and preferably about 75 wt % or less.

[0073] On the other hand, as shown in the comparative examples 8 to 10, when the Mo content reaches 29 wt %, that is, less than 30 wt %, the hardness does not satisfy the reference value Hv=600, which might result in a hard layer not sufficiently having properties that are the object of the invention. Accordingly, the Mo content is acceptably more than 29 wt % and preferably about 30 wt % or more.

[0074] From the above, the Mo content is acceptably more than 29 wt % and less than 76 wt % and preferably about 30 to 75 wt %. When the Mo content satisfies this condition, a film to be formed is acceptable on all of the four evaluation items as shown in the first objective examples, resulting in a more preferable soft metal and decorative article of wristwatch that are the object of the invention.

[0075] B) The Case of Using a Zr—Mo Additive Element Alloy

[0076] This case is shown in Table 2 and Table 3. As shown in examples 13 to 46 in Table 2 and examples 57 to 66 in Table 3, the hardness is Hv=610 or more. Further, the average surface roughness Ra is 0.35 μm or less, and the peeling starting load is 500 gf or more. All the examples have “no” corrosion. Accordingly, the examples shown in Table 2 and the examples 57 to 66 shown in Table 3 (hereinafter referred to as “second objective examples”) are acceptable in overall evaluation. The second objective examples are compared with comparative examples 11 to 20 shown in Table 3, reaching the following understanding.

[0077] Also in this case, it is only required to increase the Mo content in order to make the film higher in hardness. However, as shown in the comparative examples 11 to 14, when the Mo content reaches 66 wt%, that is, more than 65 wt%, the average surface roughness Ra becomes 0.45 μm. In this event, a hard layer is formed, in which crystalline Mo₂Zr is formed and the crystal grain boundary bulges up, presenting a lot of surface roughness. Therefore, that hard layer might affect the decorativeness of the external appearance of the soft metal and decorative article of wristwatch. Accordingly, the Mo content is acceptably less than 66 wt% and preferably about 65 wt% or less.

[0078] On the other hand, as shown in the comparative examples 15 to 17, when the Mo content reaches 24 wt %, that is, less than 25 wt %, the hardness does not satisfy the reference value Hv=600, which might result in a hard layer not sufficiently having properties that are the object of the invention. Accordingly, the Mo content is acceptably more than 24 wt % and preferably about 25 wt % or more.

[0079] From the above, the Mo content is acceptably more than 24 wt % and less than 66 wt% and preferably about 25 to 65 wt %.

[0080] When the total content of additive elements reaches 26 wt %, that is, more than 25 wt % as shown in comparative examples 18 to 20 even if the Mo content satisfies the above described condition, the average surface roughness Ra becomes 0.45 μm. Also in this case, a hard layer is formed, in which crystalline Mo₂Zr is formed and the crystal grain boundary bulges up, presenting a lot of surface roughness. Therefore, that hard layer might affect the decorativeness of the external appearance of the soft metal and decorative article of wristwatch. Accordingly, the total content of additive elements is acceptably less than 26 wt % and preferably about 25 wt % or less.

[0081] Further, focusing attention on the total content of Mo and additive elements, the results are as follows. As shown in the comparative examples 11 to 14, when the total content of Mo and additive elements reaches 81 wt %, that is, more than 80 wt %, the average surface roughness Ra becomes 0.45 μm, in which crystalline Mo₂Zr is formed and the crystal grain boundary bulges up, presenting a lot of surface roughness. Besides, as shown in the comparative examples 15 to 17, when the total content of Mo and additive elements reaches 29 wt %, that is, less than 30 wt %, the hardness does not satisfy the reference value Hv=600, which might result in a hard layer not sufficiently having properties that are the object of the invention. Within a range of the total content of Mo and additive elements of 80 wt % or less and more than 55 wt %, Mo₂Zr is formed in the hard layer but the crystal grain boundary does not coarsen, presenting little or no surface roughness. Accordingly, the total content of Mo and additive elements is acceptably more than 29 wt % and less than 81 wt % and preferably about 30 to 80 wt %.

[0082] In summary, in the case of the hard layer made of a Zr—Mo additive element alloy, when the following conditions a) and b) are satisfied, or when the condition c) is satisfied, a preferable soft metal and decorative article of wristwatch that are the object of the invention can be obtained.

[0083] a) The Mo content is more than 24 wt % and less than 66 wt%, and the Mo content is preferably about 25 to 65 wt %.

[0084] b) The total content of additive elements is less than 26 wt % and preferably about 25 wt % or less.

[0085] c) The total content of Mo and additive elements is more than 29 wt % and less than 81 wt %, and the total content of Mo and additive elements is preferably about 30 to 80 wt %.

[0086]4) Second Examples of the Soft Metal and the Decorative Article of Wristwatch

[0087] For the above-described soft metal and decorative article of wristwatch, examples (samples) having a hard layer in the amorphous phase were produced by devising the composition of the alloy target. For the soft metal as the material, two kinds of metals were used, that is, stainless steel (SUS 304) and brass when the alloy target 4 is a Zr—Mo alloy, and four kinds of metals were used, that is, stainless steels (SUS 304and SUS316L), titanium, and brass when the alloy target 4 is a Zr—Mo additive element alloy. In any case, the soft metal articles were flat plate-shaped soft metal articles and the decorative articles of wristwatch were wristwatch cases, bezels, wristwatch bands, and case backs.

[0088] Further, with each of the produced soft metals and decorative articles of wristwatch, crystallinity of the formed film was checked in addition to the above-described evaluation items. As for the crystallinity, measurement by the X-ray diffraction (θ−2θ method) was conducted making an evaluation such that the film showing a broad peak typical of an amorphous alloy was determined as being in the amorphous phase while the film showing a crystal peak as observed was determined as being in the crystalline phase. The evaluation results are as follows.

[0089] A) The Case of Using a Zr—Mo Alloy

[0090] This case is shown in Table 4. As described above, the hard layers both in the crystalline phase and the amorphous phase have properties of being high in Vickers hardness and mechanical strength and having no corrosion at all even if they are brought into contact with a substance exhibiting acidity or alkalinity. Accordingly, a preferable soft metal and decorative article of wristwatch that are the object of the invention can be obtained even with any evaluation of the crystallinity. The hard layer, however, comes to have a mirror surface into a smooth film similar to the film formed by the CVD method when its crystallinity is in the amorphous phase, and thus has a property that even if touched with a finger, the surface is insusceptible to a fingerprint left thereon. Accordingly, when the hard layer is in the amorphous phase, the layer can make the soft metal and decorative article of wristwatch better in decorativeness of the external appearance to provide a high-class feeling, resulting in a preferable decorative article especially for a wristwatch.

[0091] As shown in examples 203 to 216, when the Mo content is 30 wt % or more and 60 wt % or less, the examples are acceptable in overall evaluation, in which the film (hard layer) is in the amorphous phase. On the other hand, as in examples 201 and 202, when the Mo content is more than 60 wt %, the examples are acceptable in overall evaluation, but crystalline Mo₂Zr is formed so that the hard layer is in the crystalline phase. Since there might be a case that is not acceptable in overall evaluation when the Mo content is less than 30 wt %, the Mo content is preferably about 30 wt % or more. When the Mo content is about 30 to 60 wt %, no crystalline Mo₂Zr is formed, so that the hard layer is in the amorphous phase. Therefore, to form the hard layer in the amorphous phase, the Mo content is preferably about 30 to 60 wt %.

[0092] B) The Case of Using a Zr—Mo Additive Element Alloy

[0093] This case is shown in Table 5. As shown in examples 304 to 348, when the total content of Mo and additive elements is 30 to 55 wt %, the examples are acceptable in overall evaluation in which the film (hard layer) is in the amorphous phase. On the other hand, as in examples 301, 302, and 303, when the total content of Mo and additive elements is more than 55 wt %, the examples are acceptable in overall evaluation, but crystalline Mo₂Zr is formed so that the hard layer is in the crystalline phase. Since there might be a case that is not acceptable in overall evaluation when the total content of Mo and additive elements is less than 30 wt %, the total content of Mo and additive elements is preferably about 30 wt % or more. When the total content of Mo and additive elements is about 30 to 55 wt %, no crystalline Mo₂Zr is formed, so that the hard layer is in the amorphous phase. Therefore, to form the hard layer in the amorphous phase, the total content of Mo and additive elements is preferably about 30 to 55 wt %.

Second Embodiment

[0094] 1) A Structure of a Soft Metal and a Method of Producing the Same

[0095]FIG. 7 is an enlarged schematic sectional view showing the principal part of a soft metal 20 according to the invention, and FIG. 8 is a similar enlarged schematic sectional view showing the principal part of a soft metal 22. The soft metal 20 is composed of a soft metal portion 2, an intermediate hard layer 7 formed on the surface of the soft metal portion 2, and a hard layer 3 formed through the intermediate hard layer 7. The soft metal 22 is composed of a soft metal portion 2, an intermediate hard layer 7 formed on the surface of the soft metal portion 2, and a hard layer 13 formed through the intermediate hard layer 7. In short, the soft metals 20 and 22 have configurations that are different from those of the above-described soft metals 1 and 15 in that the respective hard layers 3 and 13 are formed through the intermediate hard layers 7, and are the same in other points.

[0096] The intermediate hard layer 7 is made of an alloy containing at least one selected from iron, cobalt, and nickel, which is a cobalt(Co)-zirconium(Zr) alloy or a cobalt(Co)-niobium(Nb)-zirconium(Zr) alloy in this embodiment. When the hard layers 3 or 13 are formed through the intermediate hard layers 7, the hard layers 3 or 13 are formed on the surfaces of the soft metals 20 and 22 together with the intermediate hard layers 7, so that the surfaces of the soft metals 20 and 22 are further increased in hardness as compared with those of the soft metals 1 and 15 and improved in abrasion resistance, so as to be insusceptible to scratches. The intermediate hard layers 7, however, are formed on the surfaces of the soft metals 20 and 22 and thus susceptible to the material thereof. Accordingly, there might be a case that the surface of the soft metal does not increase in hardness even if the intermediate hard layer is formed thereon, depending on the material (in the case of brass, Al, or the like which are softer among soft metals) of the soft metal.

[0097] The intermediate hard layer 7 may be an alloy having the following composition besides the above-described Co—Zr alloy or Co—Nb—Zr alloy. Specifically, the intermediate hard layer 7 may be made of a Fe—Co—Ni—Zr—B alloy, a Fe—Cr—Ni—Zr—B alloy, a Fe—Co—Ni—Nb—Zr—B alloy, a Fe—Co—Ni—Ta—Zr—B alloy, a Fe—Co—Cr—Ni—Nb—Zr—B alloy, a Fe—Co—Cr—Ni—Ta—Zr—B alloy, a Co—Nb—Ti alloy, a Co—Cr alloy, a Co—Ti alloy, Co—Nb alloy, a Co—Ta alloy, a Co—W alloy, a Co—Fe—Nb alloy, a Co—Ni—Nb alloy, a Co—Fe—Zr alloy, a Co—Ni—Zr alloy, a Co—Fe—Nb—Zr alloy, and a Co—Ni—Nb—Zr alloy in any composition.

[0098] Further, the intermediate hard layer 7 itself has a function of hardening the surfaces of the soft metals 20 and 22. However, since the intermediate hard layer 7 may contain Co and/or Ni that may cause metal allergy, the intermediate hard layer 7 simply formed on the surface of the soft metal may unintentionally decrease the anti-allergic property of the soft metal for a human body, leading to an unpreferable condition. In contrast, Zr, Nb, Ta, and Ti forming the hard layers 3 and 13 are harmless to a human body on the metal allergic reaction, and Mo is also an element causing no allergic reaction. Therefore, the formation of the hard layer 3 or 13 on the surface of the intermediate layer 7 can enhance the abrasion resistance and corrosion resistance without a decrease in the anti-allergic property of the soft metal for a human body.

[0099] Next, structures of the soft metals 20 and 22, methods of producing the same, and effects of the same are described in detail. It should be noted that the soft metal 20 and the soft metal 22 are different-only in composition of the hard layer formed on the surface and are the same in the other structure and method of producing the same, and therefore they are described by taking an example of a soft metal article 25 described hereinafter.

[0100] The soft metal article 25 is produced by forming a hard layer 3 or a hard layer 13 on the surface of a soft metal article 6 through an intermediate hard layer 7, and the soft metal article 25 having the hard layer 3 formed thereon corresponds to the soft metal 20, and the soft metal article 25 having the hard layer 13 formed thereon corresponds to the soft metal 22.

[0101] The soft metal article 25 is produced in the following manner.

[0102] As shown in FIG. 11, the soft metal article 6 and an alloy target 14 are first disposed inside a vacuum apparatus 100. The alloy target 14 is, for example, a Co—Zr alloy or a Co—Nb—Zr alloy. Subsequently, the vacuum apparatus 100 is evacuated through a pump 101, and thereafter, an inert gas is introduced therein and an internal pressure is maintained in the order of 3 ×10⁻³ Torr (about 0.4 Pa), and an inert gas plasma is caused to occur. In such an inert gas plasma atmosphere, a film made of metals constituting the alloy target 14 is formed on the surface of the soft metal article 6 by a sputter method. This forms the intermediate hard layer 7. Subsequently, an alloy target 4 as a second alloy target is disposed inside the vacuum apparatus 100. As the alloy target 4, a Zr—Mo alloy or a Zr—Mo additive element alloy is used. Subsequently, the internal pressure is maintained in the order of 3×10⁻³ Torr (about 0.4 Pa), and an inert gas plasma is caused to occur, and a film made of metals constituting the alloy target 4 is formed on the surface of the intermediate hard layer 7 in the inert gas plasma atmosphere by the sputter method, resulting in the soft metal article 25. Note that the use of the Zr—Mo alloy for the alloy target 4 results in the soft metal article 25 having the hard layer 3 formed on the surface thereof, and the use of the Zr—Mo additive element alloy results in the soft metal article 25 having the hard layer 13 formed on the surface thereof.

[0103] 2) A Structure of a Decorative Article of Wristwatch and a Method of Producing the Same

[0104] Next, a structure of a decorative article of wristwatch and a method of producing the same are described. FIG. 9 is a schematic sectional view showing a wristwatch case 18 being an example of a decorative article of wristwatch according to the invention and an enlarged principal part thereof, and FIG. 10 is a similar schematic sectional view showing a wristwatch case 28 and an enlarged principal part thereof. The wristwatch case 18 has the above-described hard layer 3 formed on the surface of a metal decorative base material 12 through the intermediate hard layer 7, and the wristwatch case 28 has the hard layer 13 formed on the surface of a metal decorative base material 12 through the intermediate hard layer 7.

[0105] The wristwatch cases 18 and 28 are high in abrasion resistance and rendered more insusceptible to scratches on the surface, as compared with the wristwatch cases 16 and 26, owing to the hard layers 3 or 13 formed thereon through the intermediate hard layers 7 similarly to the soft metals 20 and 22. Therefore, the wristwatch cases 18 and 28 are of high quality in terms of decorativeness of the external appearance and thus are preferably used to provide a high-class feeling to the external appearance for a wristwatch. Since the wristwatch cases 18 and 28 are apt to come into contact with a human body especially when used for a wristwatch, it is important to form the hard layers 3 or 13 on the intermediate hard layers 7 to prevent a decrease in the anti-allergic property for a human body. In this respect, the wristwatch cases 18 and 28 are useful.

[0106] The wristwatch cases 18 and 28 are produced using the metal decorative base material 12 having a shape of a wristwatch case in the same method as that of the soft metal article 25. More specifically, as shown in FIG. 12, the metal decorative base material 12 and an alloy target 14 as a first target are disposed inside a vacuum apparatus 100. As the alloy target 14, a Co—Zr alloy and a Co—Nb—Zr alloy are prepared respectively. Subsequently, the vacuum apparatus 100 is evacuated through a pump 101, thereafter, an inert gas is introduced therein and an internal pressure is maintained at a plasma generable pressure (in the order of 3×10⁻³ Torr (about 0.4 Pa)), and an inert gas plasma is caused to occur. In such an inert gas plasma atmosphere, a film made of metals constituting the alloy target 14 is formed on the surface of the metal decorative base material 12 by a sputter method, thereby forming the intermediate hard layer 7. Subsequently, an alloy target 4, as a second alloy target, is disposed inside the vacuum apparatus 100. As the alloy target 4, a Zr—Mo alloy or a Zr—Mo additive element alloy is used. Then, the internal pressure is maintained in the order of 3×10⁻³ Torr (about 0.4 Pa), and an inert gas plasma is caused to occur, and a film of metals constituting the alloy target 4 is formed on the surface of the intermediate hard layer 7 in the inert gas plasma atmosphere by the sputter method. Consequently, the hard layer 3 or 13 is formed on the surface of intermediate layer 7, resulting in the wristwatch case 18 or 28 having the hard layers 3 or 13 formed through the intermediate layer 7. Here, the use of the Zr—Mo alloy for the alloy target 4 results in the wristwatch case 18, and the use of the Zr—Mo additive element alloy results in the wristwatch case 28.

[0107] 3) First Examples of the Soft Metal and the Decorative Article of Wristwatch

[0108] Concrete examples (samples) of the above-described soft metal and decorative article of wristwatch were produced. Those examples are described with reference to Table 6 to Table 8 and a part of Table 3 again. The soft metal articles 25 were produced here according to the above-described procedure using a flat plate-shaped soft metal article as shown in FIG. 14. In this event, for the soft metal as the material, three kinds of metals, that is, Ti, brass, and aluminum (Al) and stainless steels (SUS304and SUS316L) were used. As the alloy target 4, several kinds of Zr—Mo alloys and Zr—Mo additive element alloys were prepared respectively by appropriately changing the composition of the respective metals.

[0109] As the decorative articles of wristwatch, in addition to the above-described wristwatch cases 18 and 28, several kinds of bezels, wristwatch bands, case backs, and clasps were prepared using appropriate soft metals from among those similar to the soft metal articles 25. As the alloy target 4, several kinds of Zr—Mo alloys and Zr—Mo additive element alloys were prepared respectively by appropriately changing the composition of the respective metals.

[0110] Further, to check the influence of a change in material of the soft metal on the hardness of each of the soft metals and decorative articles of wristwatch, the examples were prepared in which materials of soft metals are the same as and different from those of the examples shown in Table 1 having no intermediate hard layers.

[0111] Then, the above examples of the soft metal articles 25 and decorative articles of wristwatch were subjected to evaluation on the above-described items according to the same procedure as that of the first embodiment. The evaluation results are as follows.

[0112] A) The Case of Using a Zr—Mo Alloy

[0113] This case is shown in Table 6. In any of the examples having acceptable result in overall evaluation (examples 67 to 84), the Mo content is 30 to 75 wt %. However, when the Mo content is without this range, there arises superiority or inferiority in the evaluation items among the properties of the hard layers as in the first embodiment (see Table 3).

[0114] More specifically, when the Mo content is less than 30 wt % as in the comparative examples 8 to 10, the hardness of the hard layer formed decreases to be lower than the reference value and might not provide a soft metal and decorative article of wristwatch having properties that are the object of the invention. Besides, as shown in the comparative examples 5 to 7, when the Mo content is more than 75 wt %, a hard layer is formed, in which crystalline Mo₂Zr is formed and the crystal grain boundary bulges up, presenting a lot of surface roughness. Therefore, that hard layer might affect the decorativeness of the external appearance of the soft metal and decorative article of wristwatch. Within a range of the Mo content 75 wt % or less and more than 60 wt %, Mo₂Zr is formed in the hard layer, but the crystal grain boundary never coarsens, presenting little or no surface roughness.

[0115] The difference in hardness depending on the presence or absence of the intermediate hard layer 7 is discussed here by comparing the examples shown in Table 1 with those in Table 6.

[0116] In the examples 4 to 6 and 7 to 9 shown in Table 1, the materials of the soft metals are Ti, and the hardnesses thereof are Hv=730, 680, 650 and Hv=940, 920, 780 respectively. In contrast, in the examples 82 to 84 and 67 to 69 shown in Table 6, the materials of the soft metals are the same Ti, but the hardnesses thereof are Hv=750, 690, 680 and Hv=940, 940, 820 respectively. Since the examples 4 to 6 and 7 to 9 shown in Table 1 are the same in composition of the hard layer as the examples 82 to 84 and 67 to 69 shown in Table 6, it would be understood that when the material of the soft metal is Ti, the hardness is kept at the same or increased, even slightly, owing to the formation of the intermediate hard layer 7.

[0117] On the other hand, when the intermediate hard layer 7 was formed with the material of the soft metal changed from Ti to Al, the difference is as follows. In the examples 76 to 78 and 73 to 75 shown in Table 6, the hardnesses thereof are Hv=690, 760, 620 and Hv=890, 880, 760 respectively. Therefore, it would be understood that when the intermediate hard layer 7 is formed with the material of the soft metal changed from Ti to Al, the hardness might not increase. It can be considered that this is because the intermediate hard layer 7 is susceptible to the material of the soft metal, and Al and brass that are softer among the soft metals lead to such results.

[0118] In summary, the Mo content is acceptably more than 29 wt % and less than 76 wt % and preferably about 30 to 75 wt %. When the Mo content satisfies this condition, a more preferable soft metal and decorative article of wristwatch that are the object of the invention can be obtained. Further, to enhance the abrasion resistance by forming the intermediate hard layer, the soft metal is preferably Ti, stainless steel, or the like that are relatively hard.

[0119] B) The Case of Using a Zr—Mo Additive Element Alloy

[0120] This case is shown in Table 7 and Table 8.

[0121] As shown in the above-described comparative examples 11 to 17, when the Mo content reaches 24 wt % or 66 wt%, that is, less than 25 wt % or more than 65 wt%, there is a case not satisfying the reference value among the evaluation items (hardness or surface roughness) as in the first embodiment. In this case, crystalline Mo₂Zr is formed and the crystal grain boundary bulges up, presenting a lot of surface roughness. Therefore, to obtain a preferable soft metal and decorative article of wristwatch that are the object of the invention, the Mo content is acceptably more than 24 wt % and less than 66 wt%, and the Mo content is preferably about 25 wt % to 65 wt %.

[0122] On the other hand, as shown in the comparative examples 18 to 20, there are cases in which the Mo content is about 25 to 65 wt % but the average surface roughness Ra becomes 0.45 μm, and therefore, to eliminate this case, the total content of additive elements is acceptably less than 26 wt % and preferably about 25 wt % or less as in the first embodiment.

[0123] Besides, when the overall evaluation is acceptable, the total content of Mo and additive elements is 30 to 80 wt % as shown in Table 7, Table 8, and the examples 57 to 66 in Table 3, while when the total content of Mo and additive elements is without this range as shown in the comparative examples 11 to 17, there is a case not satisfying the reference value among the evaluation items (hardness or surface roughness). Accordingly, the total content of Mo and additive elements is acceptably more than 29 wt % and less than 81 wt % and preferably about 30 to 80 wt %.

[0124] In summary, in the case of the hard layer made of a Zr—Mo additive element alloy, when the following conditions d) and e) are satisfied, or when the condition f) is satisfied, a preferable soft metal and decorative article of wristwatch that are the object of the invention can be obtained.

[0125] d) The Mo content is more than 24 wt % and less than 66 wt%, and the Mo content is preferably about 25 to 65 wt %.

[0126] e) The total content of additive elements is less than 26 wt % and preferably about 25 wt % or less.

[0127] f) The total content of Mo and additive elements is more than 29 wt % and less than 81 wt %, and the total content of Mo and additive elements is preferably about 30 to 80 wt %.

[0128] 4) Second Examples of the Soft Metal and the Decorative Article of Wristwatch

[0129] Also in this embodiment, conditions for the hard layer to be in the amorphous phase examined on the above-described soft metal and decorative article of wristwatch according to the same procedure as that of the first embodiment are as follows.

[0130] In the case of using a Zr—Mo alloy, when the Mo content is about 30 to 60 wt %, the hard layer is in the amorphous phase. Meanwhile, in the case of using a Zr—Mo additive element alloy, when the total content of Mo and additive elements is about 30 to 55 wt %, the hard layer is in the amorphous phase. In these cases, the surface of the soft metal and decorative article of wristwatch are made smooth and thus insusceptible to a fingerprint left thereon, and can make them better in decorativeness to provide a high-class feeling. Especially, the decorative article of wristwatch becomes preferable for a wristwatch.

Third Embodiment

[0131] 1) A Structure of a Decorative Article of Wristwatch and a Method of Producing the Same

[0132]FIG. 21 is a schematic sectional view showing the internal structure of a radio controlled wristwatch 30 using a wristwatch case 31 and a case back 33 that are examples of the decorative article of wristwatch according to the invention. The radio controlled wristwatch 30 comprises the wristwatch case 31, a glass 32 fixed to the top face thereof, and the case back 33 which form a sealed space, and includes wristwatch hands 34, a dial 35, a movement 36, an antenna 37, and a terminal board 44 in the sealed space.

[0133] The radio-controlled wristwatch 30 is a radio adjustable type wristwatch that automatically adjusts the time via a predetermined time radio wave. Therefore, the wristwatch incorporates the antenna 37 for receiving the radio of time. When articles made of metal (metal articles) are arranged near the antenna 37, the metal articles may attenuate the time radio wave and cause reception fault, and therefore decorative articles of wristwatch for the radio-controlled wristwatch, that is, the wristwatch case 31 and the case back 33 in the case of the radio-controlled wristwatch 30, are generally produced using an insulating material such as resin, ceramics or the like.

[0134] The wristwatch case 31 and the case back 33, as shown in FIG. 15 and FIG. 16 respectively, have a hard layer 3 on the entire outer surface of an insulating decorative base material 52, the hard layer 3 being a metal film containing Zr and Mo as in the above-described respective embodiments. In place of the hard layer 3, a hard layer 13 may be formed that contains Zr and Mo and further an additive element comprising at least one or more elements selected from Nb, Ta, and Ti. Since Zr, Mo, Nb, Ta, and Ti have no magnetism and are low in electric conductivity, they are elements that scarcely cause radio reception fault. Accordingly, formation of the hard layer 3 or 13 composed of these metals on the entire outer surface of the insulating decorative base material 52 provides decorative articles of wristwatch that are very effective especially for the radio-controlled wristwatch. Such decorative articles of wristwatch include a bezel in addition to the wristwatch case 31 and the case back 33.

[0135] Besides, there is a technique relating to the invention that produces a wristwatch case for a radio-controlled wristwatch through coating by spraying paint in which metal powder is dispersed onto the surface of a resin molding. There is another technique that produces a wristwatch case for a radio-controlled wristwatch by forming a metal thin film made of Au, Ag, Pd, Pt, Cr, Ni, Cu, or the like on the surface of a case base body made of ceramics (for example, in JP, 2001-305244, A). The former is conducted by coating and thus has difficulty in providing a high-class feeling to the external appearance of the wristwatch case and also has a problem in adhesion of the coating film. Meanwhile, the latter can provide a high-class feeling to the external appearance of the wristwatch case but may decrease the reception sensitivity of the antenna due to the influence of the material and the film thickness of the metal thin film. The wristwatch case 31 and the case back 33 according to the invention, however, are made using the elements that have no magnetism and are low in electric conductivity as the elements constituting the hard layer as described above, so that the decrease in the reception sensitivity of the antenna 37 is limited to fall within an allowable range. Besides, the film thickness of the hard layer limited to fall within a necessary range can decrease the influence on the reception sensitivity and is preferable also in the following points.

[0136] More specifically, the hard layers 3 and 13 preferably have a film thickness in the order of about 0.05 μm to about 3 μm. This is because, with a film thickness of less than 0.05 μm, the wristwatch case 31 and the case back 33 are difficult to have an external appearance looking metallic color (hereinafter referred to as “metallic external appearance”) and are low in abrasion resistance and insufficient in durability, and with more than 3 μm, surface roughness might occur due to the stress during the film formation. The hard layer 3 (including the hard layer 13) is formed to have a small film thickness as compared with the size of the insulating decorative base material 52.

[0137] The insulating decorative base material 52 is made of an insulating material, for example, a thermoplastic resin that has been conventionally in wide use, produced in the shape corresponding to the wristwatch case 31 and the back 33. For the insulating decorative base material 52, a thermoplastic resin having heat resistance of about 200° C. or higher can be used. Specific examples of the resin include engineering plastics such as nylon, polybutylene terephthalate, and the like, or super engineering plastics such as polyphenylene sulfide, polyethersulfone, polyarylate, and the like. Further, for the purpose of enhancing the heat resistance and the mechanical strength, it is adoptable to use for the insulating decorative base material 52 a resin to which reinforcing substance such as carbon fiber, glass fiber, or the like is added. In addition, the wristwatch case 31 and the case back 33 are made for a wristwatch, for which a resin may be used in which powder of metal with a large specific gravity such as tungsten (W) or the like is dispersed to provide a feeling of depth. However, as the powder to be dispersed in the resin to increase the specific gravity, it is preferable to use powder that is a non-magnetic substance in consideration of a radio wave reception performance of the antenna 37.

[0138] Further, it is also adoptable to use ceramics, glass, or the like for the insulating decorative base material 52. As the ceramics material, zirconia, alumina, or the like can be used here, among which zirconia is especially preferable because of its superiority in impact resistance and tenacity.

[0139] The wristwatch hands 34 are constituted of a second hand 38, a minute hand 39, and an hour hand 40 which are supported by a hand shaft 41 to rotate individually on the dial 35. The dial 35 is formed of an insulator such as resin, ceramics, or the like having a surface printed or embossed with letters or the like indicating time. The movement 36 includes therein a time keeping circuit and a step motor and a train wheel for moving the wristwatch hands 34, arid is additionally provided with circuits corresponding to functions to be provided in the radio-controlled wristwatch 30, a reception circuit for receiving the radio wave of time signal through the antenna 37, a display adjustment circuit for adjusting time based on the received signal, and so on. The antenna 37 is connected to the reception circuit in the movement 36 through the terminal board 44.

[0140] It should be noted that the radio-controlled wristwatch 30 uses a packing 42 and a packing 43 for the wristwatch case 31, the glass 32, and the case back 33 to form the sealed space. The packing 42 is interposed between the wristwatch case 31 and the case back 33 and is arranged so as to close the gap between them. The packing 43 is interposed between the wristwatch case 31 and the glass 32 and is arranged so as to close the gap between them.

[0141] Next, methods of producing the wristwatch case 31 and the case back 33, and effects of the same are described in detail.

[0142] The wristwatch case 31 and the case back 33 are produced, for example, in the following manner.

[0143] First, in the case of using a thermoplastic resin, the thermoplastic resin is injected to fill molds having cavities corresponding to the respective shapes of the wristwatch case 31 and the case back 33, thereby producing the insulating decorative base materials 52, that is, the insulating moldings for obtaining the wristwatch case 31 and the case back 33. The use of the thermoplastic resin in producing the insulating decorative base materials 52 can easily provide decorative articles of wristwatch in various designs.

[0144] Further, methods of producing the insulating decorative base material 52 using ceramics include a slip casting method and a powder injection molding method. In the slip casting method, ceramics powder is dispersed in a solvent into slurry, and resulting slip is poured into a mold made of plaster or the like, released from the mold, dried and then fired to obtain a fired body. In the powder injection molding method, production is performed as follows. First, ceramics powder and an organic binder composed of a thermoplastic resin are mixed to create a composition for injection molding, which is injected to fill a mold having a cavity in the shape of a desired article to obtain a molding. Then, the molding is heated up to the order of about 400° C. to 500° C. in an atmospheric air or an inert atmosphere for degreasing, thereby removing the organic binder. Subsequently, the resulting molding is subjected to firing in the atmospheric air at a predetermined temperature, resulting in a fired body.

[0145] Then, the fired body obtained by either of the above methods is subjected to machining such as grinding of details and polishing of the surface into a desired shape of a decorative article of wristwatch, whereby the insulating decorative base material 52 made of ceramics can be produced.

[0146] Next, the hard layer 3 or the hard layer 13 is formed on the surface of the obtained insulating decorative base material 52 according to the following procedure. The insulating decorative base material 52 and an alloy target are first disposed inside the above-described vacuum apparatus, and after the vacuum apparatus is evacuated, an inert gas (for example, Ar gas) is introduced therein, and an inert gas plasma (for example, Ar gas plasma) is caused to occur. Then, an internal pressure is maintained in the order of 3×10⁻³ Torr (about 0.4 Pa), and an inert gas plasma is caused to occur. In the inert gas plasma atmosphere, a hard layer is formed on the surface of the insulating decorative base material 52 by a sputtering method using an alloy target (for example, an alloy target having a composition of Zr: 20 wt % and Mo: 80 wt %). Here, the use of a Zr—Mo alloy for the alloy target results in the wristwatch case 31 and the case back 33 having the hard layer 3 formed on the surface thereof, and the use of a Zr—Mo additive element results in the wristwatch case 31 and the case back 33 having the hard layer 13 formed on the surface thereof. The film thickness of the hard layers 3 and 13 can be arbitrarily controlled, for example, by changing the period of the sputtering.

[0147] In the formation of the hard layer conducted by the sputtering method, the temperature of the insulating decorative base material 52 during the film formation remains at about 100° C. to about 150° C., so that the hard layer can be formed at a relatively low temperature. Consequently, when the insulating decorative base material 52 is produced of resin, the hard layer in particular is preferably formed by the sputtering method. Further, the formation of the hard layer conducted by the sputtering method can not only facilitate the composition control of the hard layer but also improve the adhesion of the hard layer as compared with that produced by coating or deposition.

[0148] 2) First Examples of the Decorative Article of Wristwatch

[0149] Concrete examples (samples) of the above-described wristwatch case 31 and case back 33 were produced. Those examples are described with reference to Table 9. The wristwatch cases 31 and case backs 33 were produced using an insulating decorative base material 52 composed of a thermoplastic resin hagving a composition of 6-nylon: 80 wt %, glass fiber with 10 μm in diameter of fiber: 13 wt %, and CaSiO₃: 7 wt %. As the alloy target, several kinds of Zr—Mo alloys and Zr—Mo additive element alloys were prepared respectively by appropriately changing the composition of the respective metals. Each of the alloy targets was used to form the hard layer on the surface of the insulating decorative base material 52, thereby producing the wristwatch cases 31 and case backs 33. The hard layers 3 5 formed using the Zr—Mo alloys for the alloy target result in examples 401 to 408, and the hard layers 13 formed using the Zr—Mo additive element alloys for the alloy target results in examples 409 to 441. In each of the examples, the film thickness of the hard layer is set at about 1 μm.

[0150] Then, to check the characteristics of the resulting wristwatch case 31 and back 33, the radio controlled wristwatch 30 shown in FIG. 21 was produced using the wristwatch case 31 and case back 33 and subjected to an evaluation on four items, that is, “amount of decrease in reception sensitivity,” “abrasion resistance,” “hardness,” and “quality of external appearance” according to the following procedure.

[0151] As described above, the reception sensitivity of time radio wave of the antenna 37 is the important element to determine the performance of the radio-controlled wristwatch 30, and therefore it is necessary to minimize the influence exerted by the wristwatch case 31 and case back 33 on the radio wave reception sensitivity of the antenna 37. Hence, the “amount of decrease in reception sensitivity” was measured for evaluation according to the following procedure.

[0152] The measurement of the amount of decrease in the reception sensitivity is conducted by incorporating the movement 36 in the sealed space formed using the wristwatch case 31 and case back 33 and measuring the electric field intensity at reception limit with respect to a radio wave of 40 kHz in a shielded room that is shielded from an external radio wave. To check the influence of the hard layer on the reception characteristics, the measurement value when the movement 36 was incorporated and the measurement value of not incorporated movement 36 which had been measured in advance were compared to find the amount of decrease in the reception sensitivity. A case where the amount of decrease in the radio wave reception sensitivity was less than 1 decibel (dB) was regarded here as having no problem as the reception performance of the radio controlled wristwatch and thus evaluated as acceptable.

[0153] As the “abrasion resistance,” an abrasion test was conducted by scrubbing the surface of the wristwatch case 31 and case back 33 using a sand eraser, and a case where the base of the wristwatch case 31 and case back 33 was still invisible after 30 times reciprocations of the sand eraser with a load of 2 kg was determined as acceptable. Since these two items are important as the performance of the radio-controlled wristwatch 30, the wristwatch case 31 and case back 33 evaluated as acceptable on both items were determined as acceptable in overall evaluation.

[0154] Besides, as for the “hardness,” the Vickers hardness was measured under the condition of a load of 1 gf. It is preferable that the Vickers hardness is Hv=600 or more. Further, as for the “quality of external appearance,” the surface roughness states of the respective external appearances of the wristwatch case 31 and case back 33 were observed for evaluation. The results of performance of the above evaluations are as shown in Table 9.

[0155] As shown in Table 9, the amount of decrease in the radio wave reception sensitivity remained at 0.1 decibel in each example, and there was no problem found at all in the reception performance. Further, after the abrasion test, no peeling of the hard layer was recognized. Consequently, the respective examples were acceptable in overall evaluation.

[0156] The evaluation results of the Vickers hardness and the surface roughness state of the external appearance are as follows.

[0157] A) The Case of Using a Zr—Mo Alloy (Examples 401 to 408)

[0158] In this case, the Vickers hardness was Hv=600 or more except for the example 408. Besides, as for the surface roughness state of the external appearance, a slight surface roughness was recognized in the example 401 in which crystalline Mo₂Zr was formed, but the other examples had good states. The example 408 has a Mo content of 25 wt %, while the example 401 has a Mo content of 80 wt %. Accordingly, for good evaluations both in the Vickers hardness and the surface roughness state of the external appearance, the Mo content is acceptably more than 25 wt % and less than 80 wt %, and the Mo content is preferably about 30 to 75 wt %. The Mo content within this range can provide a decorative article of wristwatch that is excellent in abrasion resistance owing to a higher hardness and in surface smoothness presenting a beautiful external appearance and a metallic external appearance with a high-class feeling.

[0159] B) The Case of Using a Zr—Mo Additive Element Alloy (Examples 409 to 441)

[0160] In this case, the Vickers hardness was Hv=600 or more except for the examples 423, 432, and 441. Besides, as for the surface roughness state of the external appearance, a slight surface roughness was recognized in the examples 409, 410, 424, 425, 433, and 434 in which crystalline Mo₂Zr was formed, but the other examples had good states. The examples 423, 432, and 441 have a Mo content of 20 wt %, while the other examples have a Mo content of more than 20 wt %.

[0161] On the other hand, the examples 410, 425, and 434 have a Mo content of 70 wt %, while the other examples have a Mo content of less than 70 wt %. The examples 409, 424, and 433 have a content of additive element (Nb, Ta, and Ti, respectively) of 26 wt %, while the other examples have a content of additive element of less than 26 wt %.

[0162] From those results, for a good evaluation in the Vickers hardness, the Mo content is acceptably more than 20 wt %, and the Mo content is preferably about 25 wt % or more. Further, for good evaluations in the surface roughness state of the external appearance as well as the Vickers hardness, it is acceptable that the Mo content is less than 70 wt % and the content of additive element is less than 26 wt %, and it is preferable that the Mo content is about 65 wt% or less and the content of additive element is about 25 wt % or less.

[0163] 3) Second Examples of the Decorative Article of Wristwatch

[0164] In this example, the wristwatch cases 31 and case backs 33 were produced using an insulating decorative base material 52 different in material from that of the first examples. The insulating decorative base material 52 was formed using zirconia being ceramics, which was molded by the powder injection method. The insulating decorative base material 52 is produced in the following manner in detail. First, powder containing zirconia as a major constituent and an organic binder composed of a mix of polypropylene, polystyrene, ethylene-vinyl acetate, polybutyl methacrylate, and wax are mixed and kneaded into a molding material, and this molding material is used to produce insulating moldings for the wristwatch case and case back. Then, after the insulating molding is subjected to rough machining such as deburring or the like by machining, the molding is slowly, taking about 72 hours, increased in temperature to about 500° C. in an atmospheric air for degreasing, thereby removing the organic binder, and is further fired at about 1450° C. in the atmospheric air for about three hours, thereby obtaining a fired body. Subsequently, the fired body is subjected to machining such as grinding of details and polishing of the surface, whereby the insulating decorative base material 52 made of zirconea ceramics can be produced.

[0165] In this example, the wristwatch cases 31 and case backs 33 were produced with the film thickness of the hard layer appropriately changed within a range from 0.3 μm to 1.2 μm according to the same procedure as that in the first example though a different material is used for the insulating decorative base material 52. Each example was evaluated on the same items as those of the first examples. Further, as comparative examples, a metal film made of gold (Au) or nickel (Ni) in place of the hard layer was formed on the surface of the insulating decorative base material 52 by the sputtering method to produce wristwatch cases and case backs, with which radio-controlled wristwatches were produced and evaluated on the same items as those of the first examples. The results of these evaluations are as shown in Table 12.

[0166] As shown in Table 12, the amount of decrease in the radio wave reception sensitivity remained at 0.1 decibel in each example, and there was no problem found at all in the reception performance. Further, after the abrasion test, no peeling of the hard layer was recognized. Consequently, the respective examples were acceptable in overall evaluation. Besides, the respective examples had a Vickers hardness Hv=600 or more.

[0167] As shown in this example, the wristwatch case 31 and case back 33 do not decrease the radio wave reception sensitivity even if the film thickness of the hard layer is increased, and there is no problem found at all in the radio wave reception performance. This applies to the abrasion resistance. Accordingly, even when the hard layer is formed in any film thickness, the abrasion resistance can be improved without decrease in the radio wave reception sensitivity.

[0168] On the other hand, in comparative examples 407 to 414, since the amount of decrease in the radio wave reception sensitivity reaches 2.1 decibel (comparative example 407) even at the lowest, that is, more than 1 decibel, there is a great decrease in the reception performance. Further, after the abrasion test, no peeling of the metal film was recognized in the comparative examples 408 to 410 and 412 to 414, but peeling of the metal film was found in the comparative examples 407 and 411. It is considered that this results from insufficient abrasion resistance because the film thickness of the metal film is as small as 0.3 μm in the case of the comparative examples 407 and 411. From the above results, the comparative example 407 to the comparative example 414 were unacceptable in overall evaluation. Besides, as for the hardness, the comparative examples had a low value as compared with examples 454 to 461, failing to obtain sufficient hardness.

[0169] As shown in the comparative example 407 to the comparative example 410 and the comparative example 411 to the comparative example 414, when the metal film of Au or Ni is formed, the radio wave reception sensitivity decreases with an increase in the film thickness. Therefore, to restrain the decrease in the radio wave reception sensitivity to avoid radio wave reception fault, the metal film needs to be formed thin (for example, less than 0.3 μm). However, the metal film that is formed thin to have a thickness of less than 0.3 μm is insufficient in abrasion resistance and thus lack of durability, which may cause trouble in using the decorative article of wristwatch.

[0170] 4) Third Example of the Decorative Article of Wristwatch

[0171] Conditions for the hard layer to be in the amorphous phase examined on the above-described wristwatch case 31 and case back 33 according to the same procedure as that of the first embodiment were as follows.

[0172] In the case of using a Zr—Mo alloy, when the Mo content is about 30 to 60 wt %, the hard layer is in the amorphous phase. Meanwhile, in the case of using a Zr—Mo additive element alloy, when the total content of Mo and additive elements is about 30 to 55 wt %, the hard layer is in the amorphous phase. In these cases, the surface of the decorative article of wristwatch are made smooth and thus insusceptible to a fingerprint left thereon, and can make them better in decorativeness of the external appearance to provide a high-class feeling. Especially, the decorative article of wristwatch becomes preferable for a radio-controlled wristwatch.

Fourth Embodiment

[0173] 1) A Structure of a Decorative Article of Wristwatch and a Method of Producing the Same

[0174]FIG. 17 is an enlarged partial sectional view showing the principal part of a wristwatch case 45 being an example of the decorative article of wristwatch according to the invention. FIG. 18 is a similar enlarged partial sectional view showing the principal part of a case back 46. Both the wristwatch case 45 and the case back 46 have an intermediate layer 47 on the entire outer surface of an insulating decorative base material 52 and have a hard layer 3 through the intermediate layer 47, the hard layer 3 being a metal film containing Zr and Mo as in the above-described third embodiment. In place of the hard layer 3, a hard layer 13 may be formed.

[0175] In short, the wristwatch case 45 and case back 46 have configurations that are different from those of the above-described wristwatch case 31 and case back 33 in that the respective hard layers 3 or 13 are formed through the intermediate layers 47, and are the same in other points.

[0176] The intermediate layer 47 is preferably made of a urethane resin, aminoacrylic resin, or the like, and its film thickness is preferably in the order of about 10 μm to about 30 μm. This is because, with a film thickness of less than 10 μm, the base that is the surface of the insulating decorative base material 52 is difficult to be sufficiently smoothed, and with more than 30 μm, the quality of external appearance may deteriorate due to heat and stress generated when the hard layer is formed.

[0177] The wristwatch case 45 and case back 46 are produced in the following manner.

[0178] The insulating decorative base material 52 is produced according to the same procedure as that of the third embodiment. Then, paint containing resin necessary to form the intermediate layer 47 is applied onto the surface of the insulating decorative base material 52 by spraying or dipping and hardened by heat or irradiation of ultraviolet rays, thereby forming the intermediate layer 47. Then, through the intermediate layer 47, the hard layer 3 (hard layer 13) is formed on the surface of the insulating decorative base material 52 according to the same procedure as that of the third embodiment, resulting in the wristwatch case 45 and case back 46.

[0179] Owing to provision of the intermediate layer 47, the wristwatch case 45 and case back 46 decrease in the surface roughness of the external appearance to have better mirror surface property and can obtain a metallic external appearance in a mirror finished condition. It can be considered that this is because the surface roughness of the insulating decorative base material 52 caused by flaws of the mold or the enhancing substance such as glass fiber or the like contained in the thermoplastic resin being the material of the insulating decorative base material 52 was covered with the intermediate layer 47, so that the surface of the insulating decorative base material 52 was smoothed.

[0180] 2) First Examples of the Decorative article of Wristwatch

[0181] Concrete examples (samples) of the above-described wristwatch case 45 and case back 46 were produced. Those examples are described with reference to Table 10 and Table 11.

[0182] The wristwatch cases 45 and case backs 46 were produced using the insulating decorative base material 52 the same as that of the third embodiment. As the alloy target, several kinds of Zr—Mo alloys and Zr—Mo additive element alloys were prepared respectively by appropriately changing the composition of the respective metals. Each of the alloy targets was used to form the intermediate layer 47 on the surface of the insulating decorative base material 52 according to the following procedure, and a hard layer having a film thickness in the order of about 1 μm is formed through the intermediate layer 47, thereby producing the wristwatch cases 45 and case backs 46. Then, the resulting wristwatch cases 45 and case backs 46 were evaluated on the same items as those in the third embodiment. The results of the evaluations are as shown in Table 10.

[0183] The intermediate layer 47 is formed here in the following manner. First, the produced insulating decorative base material 52 is washed and dried, and then coated with paint containing a urethane resin by spray coating. Thereafter, the insulating decorative base material 52 is subjected to a hardening treatment through heating at a temperature of about 120° C. for about 90 minutes, thereby forming the intermediate layer 47. The film thickness of the intermediate layer 47 is about 15 μm.

[0184] Further, as comparative examples, a metal film was formed on the surface of the insulating decorative base material 52, in stead of forming the hard layer, to produce wristwatch cases and case backs, with which radio-controlled wristwatches were produced and evaluated on the same items as those of the third embodiment. The results of the evaluations are as shown in Table 11. It should be noted that metal comprising at least one selected from gold (Au), nickel (Ni), phosphorus (P), iron (Fe), chromium (Cr), platinum (Pt), and aluminum (Al) was used as the material of the metal film. In comparative examples 401 to 404 shown in Table 11, the metal film was formed by sputtering. The metal film was formed by electroplating in a comparative example 405 and by deposition in a comparative example 406.

[0185] As shown in Table 10, the amount of decrease in the radio wave reception sensitivity remained at 0.1 decibel in each example, and there was no problem found at all in the reception performance. Further, after the abrasion test, no peeling of the hard layer was recognized. Consequently, the respective examples were acceptable in overall evaluation.

[0186] The evaluation results of the Vickers hardness and surface roughness state are as follows.

[0187] The Vickers hardness was Hv=600 or more except for an example 453. Besides, as for the surface roughness state of the external appearance, a slight surface roughness was recognized in an example 448 in which crystalline Mo₂Zr was formed, but the other examples had good states. The example 453 has a Mo content of 5 wt % and a total content of additive elements of 15 wt %. Further, the example 448 has a Mo content of 70 wt % and a total content of additive elements of 15 wt %.

[0188] The wristwatch case 45 and case back 46 have configurations that are different from those of the wristwatch case 31 and case back 33 only in that the respective hard layers 3 or 13 are formed through the intermediate layers 47, and are the same in other points, and therefore it is considered that conditions for good Vickers hardness and conditions for good evaluations in the quality of external appearance as well as the Vickers hardness are the same as those shown in the first example of the third embodiment. More specifically, to improve the Vickers hardness, the Mo content is acceptably more than 20 wt %, and the Mo content is preferably about 25 wt % or more. Further, for good evaluations in the surface roughness state of the external appearance as well as the Vickers hardness, it is acceptable that the Mo content is less than 70 wt % and the total content of additive elements is less than 26 wt %, and it is preferable that the Mo content is about 65 wt% or less and the total content of additive elements is about 25 wt % or less. However, the content of the additive elements in this case is the total content of at least two selected from Nb, Ta, and Ti. The respective examples shown in Table 10 except the examples 448 and 453 satisfy these conditions.

[0189] On the other hand, as shown in Table 11, in the comparative example 401 to the comparative example 406, since the amount of decrease in the radio wave reception sensitivity reaches 1.3 decibel (comparative example 404) even at the lowest, that is, more than 1 decibel, there is a great decrease in the reception performance. Further, after the abrasion test, no peeling of the metal film was recognized in the comparative examples 401 to 404, but peeling of the metal film was found in the comparative examples 405 and 406. It is considered that this is because the metal film does not have sufficient adhesion because the metal film was formed by plating or deposition in the case of the comparative examples 405 and 406. From the above results, the comparative example 401 to the comparative example 406 were unacceptable in overall evaluation. Besides, as for the hardness, the comparative examples had a low value as compared with the examples shown in Table 10, failing to obtain sufficient hardness.

[0190] 3) Second Examples of the Decorative Article of Wristwatch

[0191] Conditions for the hard layer to be in the amorphous phase examined on the above-described wristwatch case 45 and case back 46 according to the same procedure as that of the first embodiment were as follows.

[0192] In the case of using a Zr—Mo alloy, when the Mo content is about 30 to 60 wt %, the hard layer is in the amorphous phase. Meanwhile, in the case of using a Zr—Mo additive element alloy, when the total content of Mo and additive elements is about 30 to 55 wt %, the hard layer is in the amorphous phase. In these cases, the surface of the soft metal and decorative article of wristwatch are made smooth and thus insusceptible to a fingerprint left thereon, and can make them better in decorativeness of the external appearance to provide a high-class feeling. Especially, the decorative article of wristwatch becomes preferable for a radio-controlled wristwatch.

Fifth Embodiment

[0193] 1) A Structure of a Decorative Article of Wristwatch and a Method of Producing the Same

[0194]FIG. 19 is an enlarged partial sectional view showing the principal part of a wristwatch case 48 being an example of the decorative article of wristwatch according to the invention. FIG. 20 is a similar enlarged partial sectional view showing the principal part of a case back 49. Both the wristwatch case 48 and the case back 49 have a hard layer 3 through an intermediate layer 47 on the entire outer surface of an insulating decorative base material 52, and have a protective film 50 made of a transparent resin formed on the entire surface of the hard layer 3, the hard layer 3 being a metal film containing Zr and Mo as in the above-described third embodiment. In place of the hard layer 3, a hard layer 13 may be formed, and it is also adoptable to form the hard layer 3 or the hard layer 13 not through the intermediate layer 47 and to form the protective film 50 on the entire surface thereof.

[0195] In short, the wristwatch case 48 and case back 49 have configurations that are different form those of the above-described wristwatch case 45 and case back 46 in that the protective films 50 are formed on the respective hard layers 3 or 13, and the same in other points.

[0196] The protective film 50 is formed of resin, and is preferably formed of an optically transparent resin to take full advantage of the metallic color of the hard layer 3 (hard layer 13) to be formed on the base thereof and preferably formed of resin excellent in corrosion resistance and chemical resistance as well as abrasion resistance. Specifically, it is preferable to use resin such as a urethane resin, acrylic resin, silicone resin, fluoric resin, or the like. Further, it is adoptable to color the protective film 50 by adding a pigment or the like to its material (for example, paint).

[0197] The film thickness of the protective film 50 is preferably in the order of about 5 μm to about 30 μm. This is because, with a film thickness of less than 5 μm, the protective film 50 is insufficient in abrasion resistance, and with a film thickness of more than 30 μm, the protective film lacks in smoothness to lead to a deterioration in the quality of external appearance of the wristwatch case 48 and case back 49.

[0198] The formation of the protective film on the surface of the hard layer 3 or 13 can improve the abrasion resistance of the wristwatch case 48 and case back 49. It is preferable to form the protective film 50 particularly when the film thickness of the hard layer 3 or 13 is small, for example, 0.3 μm or less. The formation of the protective film 50 can improve the abrasion resistance of the wristwatch case 48 and case back 49.

[0199] The wristwatch case 48 and case back 49 are produced as in the following manner.

[0200] The insulating decorative base material 52 made of resin or ceramics is produced according to the same procedure as that of the third embodiment. For this insulating decorative base material 52, the hard layer 3 or 13 is formed according to the same procedure as that of the third embodiment. In this event, the hard layer 3 or 13 is formed through the intermediate layer 47, but may be formed not through the intermediate layer 47. The film thickness of the hard layers 3 and 13 is preferably in the order of about 0.05 μm to about 0.3 μm. The film thickness of less than about 0.05 μm is not preferable because sufficient metallic external appearance cannot be obtained. When paint being a material of the protective film 50 is applied to the surface of the hard layer 3 or 13 by spraying or dipping and hardened by heat or irradiation of ultraviolet rays, the protective film 50 is formed, resulting in the wristwatch case 48 and case back 49.

[0201] 2) Examples of the Decorative Article of Wristwatch

[0202] Concrete examples (samples) of the above-described wristwatch case 48 and case back 49 were produced. Those examples are described with reference to Table 13.

[0203] The wristwatch cases 48 and case backs 49 were produced using the same thermoplastic resin as that of the third embodiment (for example, a thermoplastic resin having a composition of 6-nylon: 80 wt %, glass fiber with 10 μm in diameter of fiber: 13 wt %, and CaSiO₃: 7 wt %). Then, the insulating decorative base material 52 is formed according to the same procedure as that of the third embodiment. To the surface of the insulating decorative base material 52, paint containing a urethane resin is applied by spray coating and subjected to a hardening treatment through heating at a temperature of about 120° C. for about 90 minutes, thereby forming the intermediate layer 47 (having a film thickness of about 15 μm). Through the intermediate layer 47, the hard layer 13 was formed, thereby producing the wristwatch cases 48 and case backs 49. The intermediate layer 47 is formed to have here a film thickness of 15 μm, and the hard layer 13 is formed to have a film thickness of 0.1 μm. Further, three different protective films 50 were formed on the surface of the hard layers 13.

[0204] First of all, paint containing an acrylic resin was applied by spray coating and then left standing at room temperature for about 24 hours, thereby forming a protective film 50 having a film thickness of 25 μm (example 462). Further, paint containing a urethane resin was applied by spray coating and then dried at about 70° C. for about 90 minutes, thereby forming a protective film 50 having a film thickness of 20 μm (example 463). Furthermore, ultraviolet curing paint containing a silicone resin was applied by spray coating and subjected to a hardening treatment by irradiating with ultraviolet rays having a wavelength of 365 μm, thereby forming a protective, film 50 having a film thickness of 10 μm (example 464).

[0205] Further, the wristwatch case and case back were produced (comparative examples 415 and 416) according to the same procedure as that of the example 462 except that the film thickness of the protective film was changed (3 μm and 40 μm). Furthermore, the wristwatch case and case back were produced (comparative example 417) according to the same procedure as that of the example 463 except that the film thickness of the hard layer was changed (0.03 μm).

[0206] Then, the resulting wristwatch cases and case backs were evaluated on the above-described items as those of the third embodiment except the hardness. The evaluation results are as shown in Table 13.

[0207] As shown in Table 13, the amount of decrease in the radio wave reception sensitivity remained at 0.05 decibel in each example, and there was no problem found at all in the reception performance. Further, even though the film thickness of the hard layer is as small as 0.1 μm, no peeling of the hard layer was recognized also after the abrasion test, so that abrasion resistance thereof was good. This is because the surface of the hard layer 13 is protected by the protective film 50.

[0208] On the other hand, in the comparative example 415 and the comparative example 416, the amount of decrease in the radio wave reception sensitivity remained at 0.05 decibel, and there was no problem found at all in the reception performance. However, in the comparative example 415, peeling of the hard layer after the abrasion test was recognized, resulting in poor abrasion resistance. It is considered that this results from insufficient abrasion resistance of the protective film 50 because the film thickness of the protective film 50 is as small as 3 μm. Besides, the comparative example 416 was good in abrasion resistance but poor in quality of external appearance due to lack of smoothness because the film thickness of the protective film is as large as 40 μm. In addition, the comparative example 417 was good in abrasion resistance but poor in quality of external appearance due to lack of excellent metallic color because the film thickness of the hard layer is as small as 0.03 μm.

[0209] It should be noted that it is suitable to introduce Ar gas as the inert gas introduced into the vacuum apparatus to cause an inert gas plasma to occur in the above-described embodiments, and it is also adoptable to introduce He (helium), Ne (neon), Xe (xenon), or Kr (krypton) in place of the Ar gas. The pressure at which the inert gas is introduced into the vacuum apparatus only needs to be a pressure capable of causing an inert gas plasma to occur, and thus is not limited to the order of 3×10⁻³ Torr (about 0.4 Pa).

[0210] Further, it is possible to apply, as the sputtering, for example, RF sputtering, DC sputtering, RF magnetron sputtering, DC magnetron sputtering, and so on. TABLE 1 Surface roughness Adhesion Average property Soft metal article Composition of surface Peeling Corrosion Material of Decorative article of hard layer (wt %) Hardness roughness starting resistance Overall soft metal wristwatch Zr Mo (Hv) Ra (μm) load (gf) Corrosion evaluation Example 1 SUS316L flat plate 25 75 950 0.35 750 no acceptable Example 2 SUS316L flat plate 30 70 930 0.3 750 no acceptable Example 3 SUS316L wristwatch bezel 40 60 800 0.2 650 no acceptable Example 4 Ti wristwatch bezel 50 50 730 0.1 600 no acceptable Example 5 Ti flat plate 60 40 680 0.1 550 no acceptable Example 6 Ti flat plate 70 30 650 0.1 500 no acceptable Example 7 Ti wristwatch band 25 75 940 0.35 750 no acceptable Example 8 Ti wristwatch case 30 70 920 0.3 750 no acceptable Example 9 Ti wristwatch case back 40 60 780 0.15 650 no acceptable Example 10 SUS316L wristwatch band 50 50 740 0.1 600 no acceptable Example 11 SUS316L wristwatch case 60 40 700 0.1 600 no acceptable Example 12 SUS316L wristwatch case back 70 30 650 0.1 500 no acceptable plating film C/P ex. 1 SUS316L flat plate Ni-P plating 320 0.1 300 no unacceptable C/P ex. 2 Ti flat plate Ni-P plating 300 0.1 300 no unacceptable C/P ex. 3 SUS316L wristwatch band Ni-P plating 360 0.1 350 no unacceptable C/P ex. 4 Ti wristwatch band Ni-P plating 350 0.1 300 no unacceptable

[0211] TABLE 2 Surface roughness Adhesion Average property Material Soft metal article Composition of Hard- surface Peeling Corrosion of Decorative article of hard layer (wt %) ness roughness starting resistance Overall soft metal wristwatch Zr Mo Nb Ta Ti (Hv) Ra (μm) load (gf) Corrosion evaluation Example 13 Ti flat plate 20 65 15 900 0.3 750 no acceptable Example 14 Ti flat plate 25 60 15 920 0.3 750 no acceptable Example 15 brass flat plate 45 50 5 740 0.1 600 no acceptable Example 16 brass flat plate 40 50 10 770 0.15 650 no acceptable Example 17 SUS304 flat plate 50 49 1 730 0.1 600 no acceptable Example 18 SUS304 flat plate 50 47 3 720 0.1 600 no acceptable Example 19 Ti wristwatch case 55 40 5 700 0.1 600 no acceptable Example 20 Ti wristwatch bezel 50 40 10 740 0.1 600 no acceptable Example 21 brass wristwatch case 40 40 20 730 0.1 600 no acceptable Example 22 brass wristwatch band 50 30 20 660 0.1 550 no acceptable Example 23 SUS304 wristwatch case 70 25 5 640 0.1 500 no acceptable Example 24 SUS304 wristwatch band 50 25 25 670 0.1 550 no acceptable Example 25 Ti wristwatch case 20 65 15 940 0.35 750 no acceptable Example 26 Ti wristwatch band 45 50 5 800 0.2 700 no acceptable Example 27 brass wristwatch case 50 49 1 720 0.1 600 no acceptable Example 28 brass wristwatch band 55 40 5 710 0.1 600 no acceptable Example 29 SUS304 wristwatch bezel 40 40 20 740 0.1 600 no acceptable Example 30 SUS304 wristwatch band 70 25 5 630 0.1 500 no acceptable Example 31 SUS304 wristwatch case back 25 60 15 920 0.3 750 no acceptable Example 32 SUS304 clasp 40 50 10 750 0.15 600 no acceptable Example 33 Ti flat plate 50 47 3 710 0.1 600 no acceptable Example 34 Ti clasp 50 40 10 790 0.15 650 no acceptable Example 35 brass wristwatch case back 50 30 20 650 0.1 500 no acceptable Example 36 brass flat plate 50 25 25 630 0.1 500 no acceptable Example 37 brass wristwatch case 25 60 10 5 920 0.3 750 no acceptable Example 38 brass wristwatch band 50 40 5 5 690 0.1 550 no acceptable Example 39 SUS304 wristwatch case 45 50 2 3 800 0.2 700 no acceptable Example 40 SUS304 wristwatch band 40 50 5 5 780 0.15 650 no acceptable Example 41 SUS304 flat plate 40 50 5 5 770 0.15 650 no acceptable Example 42 SUS304 wristwatch band 40 40 10 10 750 0.15 600 no acceptable Example 43 Ti wristwatch case 50 47 1 1 1 740 0.1 600 no acceptable Example 44 Ti wristwatch band 40 40 10 5 5 700 0.1 600 no acceptable Example 45 Ti wristwatch case back 40 40 5 10 5 680 0.1 550 no acceptable Example 46 Ti clasp 40 40 5 5 10 680 0.1 550 no acceptable

[0212] TABLE 3 Surface rough- ness Average Adhesion surface property Material Soft metal article Composition of Hard- rough- Peeling Corrosion of Decorative article of hard layer (wt %) ness ness starting resistance Overall soft metal wristwatch Zr Mo Nb Ta Ti (Hv) Ra (μm) load (gf) Corrosion evaluation Example 51 Al flat plate 25 75 940 0.35 750 no acceptable Example 52 brass flat plate 25 75 960 0.35 800 no acceptable Example 53 SUS304 flat plate 25 75 950 0.35 750 no acceptable Example 54 Al wristwatch case 70 30 630 0.1 500 no acceptable Example 55 brass wristwatch case 70 30 620 0.1 500 no acceptable Example 56 SUS304 wristwatch case 70 30 640 0.1 500 no acceptable Example 57 SUS316L flat plate 20 65 15 940 0.35 750 no acceptable Example 58 Ti wristwatch case 20 65 15 950 0.35 750 no acceptable Example 59 Ti wristwatch band 20 65 15 950 0.35 750 no acceptable Example 60 Ti wristwatch case back 20 65 5 5 5 960 0.35 750 no acceptable Example 61 Al wristwatch case 70 25 5 640 0.1 500 no acceptable Example 62 brass wristwatch band 70 25 5 630 0.1 500 no acceptable Example 63 SUS316L wristwatch band 70 25 5 630 0.1 500 no acceptable Example 64 Al wristwatch case 70 29 1 620 0.1 500 no acceptable Example 65 brass wristwatch band 70 29 1 610 0.1 500 no acceptable Example 66 SUS316L wristwatch case back 70 29 1 610 0.1 500 no acceptable C/P ex. 5 Al flat plate 24 76 1040 0.45 800 no unacceptable C/P ex. 6 brass flat plate 24 76 1050 0.45 850 no unacceptable C/P ex. 7 SUS304 flat plate 24 76 1040 0.45 800 no unacceptable C/P ex. 8 Al wristwatch case 71 29 580 0.1 450 no unacceptable C/P ex. 9 brass wristwatch case 71 29 570 0.1 450 no unacceptable C/P ex. 10 SUS304 wristwatch case 71 29 560 0.1 450 no unacceptable C/P ex. 11 SUS316L flat plate 19 66 15 1040 0.45 800 no unacceptable C/P ex. 12 Ti wristwatch case 19 66 15 1040 0.45 800 no unacceptable C/P ex. 13 Ti wristwatch band 19 66 15 1040 0.45 800 no unacceptable C/P ex. 14 Ti wristwatch case back 19 66 5 5 5 1060 0.45 850 no unacceptable C/P ex. 15 Al wristwatch case 71 24 5 580 0.1 450 no unacceptable C/P ex. 16 brass wristwatch band 71 24 5 560 0.1 450 no unacceptable C/P ex. 17 SUS316L wristwatch band 71 24 5 560 0.1 450 no unacceptable C/P ex. 18 Al wristwatch case 20 54 26 1040 0.45 800 no unacceptable C/P ex. 19 brass wristwatch band 20 54 26 1050 0.45 850 no unacceptable C/P ex. 20 SUS316L wristwatch case back 20 54 26 1040 0.45 800 no unacceptable

[0213] TABLE 4 Surface roughness Adhesion Average property Material Soft metal article Composition surface Peeling Corrosion of Decorative article of of hard layer (wt %) Hardness roughness starting resistance Overall soft metal wristwatch Zr Mo (Hv) Ra (μm) load (gf) Corrosion evaluation Crystallinity Example 201 brass flat plate 35 65 920 0.3 750 no acceptable crystal phase Example 202 SUS304 flat plate 38 62 900 0.3 750 no acceptable crystal phase Example 203 brass flat plate 40 60 800 0.2 700 no acceptable amorphous phase Example 204 brass wristwatch case 45 55 760 0.15 650 no acceptable amorphous phase Example 205 brass wristwatch band 50 50 730 0.1 600 no acceptable amorphous phase Example 206 brass wristwatch bezel 55 45 700 0.1 600 no acceptable amorphous phase Example 207 brass wristwatch case back 60 40 670 0.1 550 no acceptable amorphous phase Example 208 brass wristwatch case 65 35 650 0.1 500 no acceptable amorphous phase Example 209 brass wristwatch bezel 70 30 640 0.1 500 no acceptable amorphous phase Example 210 SUS304 flat plate 40 60 820 0.2 700 no acceptable amorphous phase Example 211 SUS304 wristwatch case 45 55 770 0.15 650 no acceptable amorphous phase Example 212 SUS304 wristwatch band 50 50 750 0.1 600 no acceptable amorphous phase Example 213 SUS304 wristwatch bezel 55 45 710 0.1 600 no acceptable amorphous phase Example 214 SUS304 wristwatch case back 60 40 680 0.1 550 no acceptable amorphous phase Example 215 SUS304 wristwatch case 65 35 660 0.1 550 no acceptable amorphous phase Example 216 SUS304 wristwatch bezel 70 30 650 0.1 500 no acceptable amorphous phase

[0214] TABLE 5 Surface roughness Adhesion Average property Soft metal article Composition of Hard- surface Peeling Corrosion Material of decorative article of hard layer (wt %) ness roughness starting resistance Overall soft metal wristwatch Zr Mo Nb Ta Ti (Hv) Ra (μm) load (gf) Corrosion evaluation Crystallinity Example 301 Ti flat plate 35 40 25 760 0.15 650 no acceptable crystal phase Example 302 SUS304 flat plate 40 45 15 790 0.15 650 no acceptable crystal phase Example 303 SUS316L flat plate 43 56 1 820 0.2 700 no acceptable crystal phase Example 304 Ti wristwatch band 45 30 25 710 0.1 600 no acceptable amorphous phase Example 305 Ti wristwatch bezel 50 25 25 670 0.1 550 no acceptable amorphous phase Example 306 Ti wristwatch case back 45 35 20 740 0.1 600 no acceptable amorphous phase Example 307 Ti wristwatch case 55 25 20 670 0.1 550 no acceptable amorphous phase Example 308 SUS304 wristwatch band 45 40 15 760 0.15 650 no acceptable amorphous phase Example 309 SUS304 wristwatch bezel 55 30 15 720 0.1 600 no acceptable amorphous phase Example 310 SUS304 wristwatch case back 45 45 10 790 0.15 650 no acceptable amorphous phase Example 311 SUS304 wristwatch case 55 35 10 730 0.1 600 no acceptable amorphous phase Example 312 brass wristwatch band 60 30 10 710 0.1 600 no acceptable amorphous phase Example 313 brass wristwatch bezel 45 50 5 790 0.15 650 no acceptable amorphous phase Example 314 brass wristwatch case back 50 45 5 770 0.15 650 no acceptable amorphous phase Example 315 SUS316L wristwatch band 60 35 5 740 0.1 550 no acceptable amorphous phase Example 316 SUS316L wristwatch bezel 70 25 5 650 0.1 500 no acceptable amorphous phase Example 317 SUS316L wristwatch case back 45 54 1 790 0.15 650 no acceptable amorphous phase Example 318 SUS316L wristwatch case 70 29 1 640 0.1 500 no acceptable amorphous phase Example 319 Ti wristwatch band 45 30 25 730 0.1 600 no acceptable amorphous phase Example 320 Ti wristwatch bezel 50 25 25 700 0.1 600 no acceptable amorphous phase Example 321 Ti wristwatch case back 45 35 20 760 0.15 650 no acceptable amorphous phase Example 322 Ti wristwatch case 55 25 20 700 0.1 600 no acceptable amorphous phase Example 323 SUS304 wristwatch band 45 40 15 790 0.15 650 no acceptable amorphous phase Example 324 SUS304 wristwatch bezel 55 30 15 740 0.1 600 no acceptable amorphous phase Example 325 SUS304 wristwatch case back 45 45 10 820 0.2 700 no acceptable amorphous phase Example 326 SUS304 wristwatch case 55 35 10 750 0.15 600 no acceptable amorphous phase Example 327 brass wristwatch band 60 30 10 740 0.1 600 no acceptable amorphous phase Example 328 brass wristwatch bezel 45 50 5 810 0.2 650 no acceptable amorphous phase Example 329 brass wristwatch case back 50 45 5 800 0.2 650 no acceptable amorphous phase Example 330 SUS316L wristwatch band 60 35 5 770 0.15 650 no acceptable amorphous phase Example 331 SUS316L wristwatch bezel 70 25 5 680 0.1 550 no acceptable amorphous phase Example 332 SUS316L wristwatch case back 45 54 1 820 0.2 700 no acceptable amorphous phase Example 333 SUS316L wristwatch case 70 29 1 670 0.1 550 no acceptable amorphous phase Example 334 Ti wristwatch band 45 30 25 700 0.1 600 no acceptable amorphous phase Example 335 Ti wristwatch bezel 50 25 25 670 0.1 550 no acceptable amorphous phase Example 336 Ti wristwatch case back 45 35 20 730 0.1 600 no acceptable amorphous phase Example 337 Ti wristwatch case 55 25 20 660 0.1 550 no acceptable amorphous phase Example 338 SUS304 wristwatch band 45 40 15 750 0.15 600 no acceptable amorphous phase Example 339 SUS304 wristwatch bezel 55 30 15 710 0.1 600 no acceptable amorphous phase Example 340 SUS304 wristwatch case back 45 45 10 770 0.15 650 no acceptable amorphous phase Example 341 SUS304 wristwatch case 55 35 10 720 0.1 600 no acceptable amorphous phase Example 342 brass wristwatch band 60 30 10 700 0.1 600 no acceptable amorphous phase Example 343 brass wristwatch bezel 45 50 5 780 0.15 650 no acceptable amorphous phase Example 344 brass wristwatch case back 50 45 5 750 0.15 600 no acceptable amorphous phase Example 345 SUS316L wristwatch band 60 35 5 730 0.1 600 no acceptable amorphous phase Example 346 SUS316L wristwatch bezel 70 25 5 640 0.1 500 no acceptable amorphous phase Example 347 SUS316L wristwatch case back 45 54 1 770 0.15 650 no acceptable amorphous phase Example 348 SUS316L wristwatch case 70 29 1 630 0.1 500 no acceptable amorphous phase

[0215] TABLE 6 Surface roughness Adhesion Material Average property of Soft metal article Composition of surface Peeling Corrosion soft Decorative article Intermediate hard layer (wt %) Hardness roughness starting resistance Overall metal of wristwatch hard layer Zr Mo (Hv) Ra (μm) load (gf) Corrosion evaluation Example 67 Ti wristwatch bezel Co—Zr alloy 25 75 940 0.35 750 no acceptable Example 68 Ti wristwatch band Co—Zr alloy 30 70 940 0.35 750 no acceptable Example 69 Ti wristwatch case Co—Zr alloy 40 60 820 0.2 700 no acceptable Example 70 brass flat plate Co—Zr alloy 50 50 700 0.1 600 no acceptable Example 71 brass wristwatch band Co—Zr alloy 60 40 660 0.1 550 no acceptable Example 72 brass wristwatch case Co—Zr alloy 70 30 630 0.1 500 no acceptable Example 73 Al flat plate Co—Zr alloy 25 75 890 0.25 750 no acceptable Example 74 Al wristwatch case Co—Zr alloy 30 70 880 0.25 700 no acceptable Example 75 Al wristwatch case Co—Zr alloy 40 60 760 0.15 650 no acceptable Example 76 Al flat plate Co—Nb—Zr 50 50 690 0.1 550 no acceptable alloy Example 77 Al wristwatch case Co—Nb—Zr 60 40 760 0.15 650 no acceptable alloy Example 78 Al wristwatch case Co—Nb—Zr 70 30 620 0.1 500 no acceptable alloy Example 79 brass flat plate Co—Nb—Zr 25 75 930 0.3 750 no acceptable alloy Example 80 brass wristwatch band Co—Nb—Zr 30 70 900 0.3 750 no acceptable alloy Example 81 brass wristwatch case Co—Nb—Zr 40 60 780 0.15 650 no acceptable alloy Example 82 Ti wristwatch bezel Co—Nb—Zr 50 50 750 0.15 600 no acceptable alloy Example 83 Ti wristwatch band Co—Nb—Zr 60 40 690 0.1 550 no acceptable alloy Example 84 Ti wristwatch case Co—Nb—Zr 70 30 680 0.1 550 no acceptable alloy

[0216] TABLE 7 Surface roughness Adhesion Average property Soft metal article Composition of surface Peeling Corrosion Material of Decorative article of Intermediate hard layer (wt %) Hardness roughness starting resistance Overall soft metal wristwatch hard layer Zr Mo Nb Ta Ti (Hv) Ra (μm) load (gf) Corrosion evaluation Example 85 Al flat plate Co—Zr alloy 30 60 10 960 0.35 800 no acceptable Example 86 Al wristwatch case Co—Zr alloy 45 50 5 820 0.2 700 no acceptable Example 87 brass wristwatch case Co—Zr alloy 45 45 10 800 0.2 650 no acceptable Example 88 Ti wristwatch case Co—Zr alloy 40 40 20 810 0.2 650 no acceptable Example 89 SUS304 wristwatch case Co—Zr alloy 50 40 10 820 0.2 700 no acceptable Example 90 SUS316L wristwatch case Co—Zr alloy 50 30 20 750 0.15 600 no acceptable Example 91 brass flat plate Co—Zr alloy 30 60 10 980 0.35 800 no acceptable Example 92 Al wristwatch case Co—Zr alloy 45 50 5 790 0.15 650 no acceptable Example 93 brass wristwatch band Co—Zr alloy 45 45 10 780 0.15 650 no acceptable Example 94 Ti wristwatch bezel Co—Zr alloy 40 40 20 810 0.2 650 no acceptable Example 95 SUS304 wristwatch bezel Co—Zr alloy 50 40 10 820 0.2 700 no acceptable Example 96 SUS316L wristwatch bezel Co—Zr alloy 50 30 20 750 0.15 600 no acceptable Example 97 Al flat plate Co—Zr alloy 30 60 10 930 0.3 750 no acceptable Example 98 Al wristwatch case Co—Zr alloy 45 50 5 800 0.2 650 no acceptable Example 99 Ti clasp Co—Zr alloy 45 45 10 780 0.15 650 no acceptable Example 100 Ti wristwatch case Co—Zr alloy 40 40 20 800 0.2 650 no acceptable back Example 101 SUS304 wristwatch case Co—Zr alloy 50 40 10 820 0.2 700 no acceptable back Example 102 SUS316L wristwatch case Co—Zr alloy 50 30 20 760 0.15 650 no acceptable back Example 103 brass wristwatch band Co—Zr alloy 30 60 5 5 990 0.4 800 no acceptable Example 104 brass flat plate Co—Zr alloy 40 50 5 5 820 0.2 700 no acceptable Example 105 Ti wristwatch band Co—Zr alloy 35 50 10 5 800 0.2 650 no acceptable Example 106 Al wristwatch case Co—Zr alloy 45 40 10 5 740 0.1 600 no acceptable Example 107 Ti wristwatch band Co—Zr alloy 30 60 5 5 960 0.35 800 no acceptable Example 108 Al flat plate Co—Zr alloy 40 50 5 5 820 0.2 700 no acceptable Example 109 SUS304 wristwatch band Co—Zr alloy 35 50 10 5 810 0.2 700 no acceptable Example 110 brass wristwatch case Co—Zr alloy 45 40 10 5 740 0.1 600 no acceptable Example 111 Ti wristwatch band Co—Zr alloy 30 60 5 5 950 0.35 750 no acceptable Example 112 Ti flat plate Co—Zr alloy 40 50 5 5 820 0.2 700 no acceptable Example 113 SUS304 wristwatch case Co—Zr alloy 35 50 10 5 830 0.2 700 no acceptable back Example 114 SUS304 wristwatch case Co—Zr alloy 45 40 10 5 750 0.15 600 no acceptable back Example 115 SUS316L wristwatch band Co—Zr alloy 40 40 10 5 5 790 0.15 650 no acceptable Example 116 SUS316L wristwatch case Co—Zr alloy 40 40 5 10 5 760 0.15 650 no acceptable Example 117 SUS316L wristwatch case Co—Zr alloy 40 40 5 5 10 770 0.15 650 no acceptable back Example 118 Al flat plate Co—Nb—Zr 30 60 10 950 0.35 750 no acceptable alloy Example 119 Al wristwatch case Co—Nb—Zr 45 50 5 830 0.2 700 no acceptable alloy Example 120 brass wristwatch band Co—Nb—Zr 45 45 10 790 0.15 650 no acceptable alloy

[0217] TABLE 8 Surface roughness Adhesion Average property Soft metal article Composition of surface Peeling Corrosion Material of Decorative article of Intermediate hard layer (wt %) Hardness roughness starting resistance Overall soft metal wristwatch hard layer Zr Mo Nb Ta Ti (Hv) Ra (μm) load (gf) Corrosion evaluation Example 121 Ti wristwatch band Co—Nb—Zr 40 40 20 820 0.2 700 no acceptable alloy Example 122 brass flat plate Co—Nb—Zr 50 40 10 830 0.2 700 no acceptable alloy Example 123 brass wristwatch band Co—Nb—Zr 50 30 20 750 0.15 600 no acceptable alloy Example 124 Ti wristwatch case Co—Nb—Zr 30 60 10 960 0.35 800 no acceptable alloy Example 125 SUS304 wristwatch case Co—Nb—Zr 45 50 5 770 0.15 650 no acceptable alloy Example 126 SUS316L wristwatch case Co—Nb—Zr 45 45 10 770 0.15 650 no acceptable alloy Example 127 Al flat plate Co—Nb—Zr 40 40 20 790 0.15 650 no acceptable alloy Example 128 Al wristwatch case Co—Nb—Zr 50 40 10 810 0.2 650 no acceptable alloy Example 129 brass wristwatch band Co—Nb—Zr 50 30 20 740 0.1 600 no acceptable alloy Example 130 Ti wristwatch bezel Co—Nb—Zr 30 60 10 940 0.35 750 no acceptable alloy Example 131 SUS304 wristwatch bezel Co—Nb—Zr 45 50 5 820 0.2 700 no acceptable alloy Example 132 SUS316L wristwatch bezel Co—Nb—Zr 45 45 10 790 0.15 650 no acceptable alloy Example 133 brass wristwatch case Co—Nb—Zr 40 40 20 810 0.2 650 no acceptable alloy Example 134 brass wristwatch band Co—Nb—Zr 50 40 10 810 0.2 650 no acceptable alloy Example 135 Ti clasp Co—Nb—Zr 50 30 20 770 0.15 650 no acceptable alloy Example 136 Ti wristwatch case Co—Nb—Zr 30 60 5 5 1000 0.4 800 no acceptable back alloy Example 137 SUS304 clasp Co—Nb—Zr 40 50 5 5 830 0.2 700 no acceptable alloy Example 138 SUS316L clasp Co—Nb—Zr 35 50 10 5 820 0.2 700 no acceptable alloy Example 139 SUS304 wristwatch case Co—Nb—Zr 45 40 10 5 760 0.15 650 no acceptable back alloy Example 140 SUS304 wristwatch case Co—Nb—Zr 30 60 5 5 980 0.35 800 no acceptable alloy Example 141 SUS304 wristwatch band Co—Nb—Zr 40 50 5 5 840 0.2 700 no acceptable alloy Example 142 Ti wristwatch case Co—Nb—Zr 35 50 10 5 820 0.2 700 no acceptable alloy Example 143 Ti wristwatch band Co—Nb—Zr 45 40 10 5 770 0.15 650 no acceptable alloy Example 144 SUS316L wristwatch case Co—Nb—Zr 30 60 5 5 960 0.35 800 no acceptable back alloy Example 145 SUS316L wristwatch case Co—Nb—Zr 40 50 5 5 840 0.2 700 no acceptable alloy Example 146 SUS316L wristwatch band Co—Nb—Zr 35 50 10 5 840 0.2 700 no acceptable alloy Example 147 Ti clasp Co—Nb—Zr 45 40 10 5 770 0.15 650 no acceptable alloy Example 148 Ti wristwatch case Co—Nb—Zr 40 40 10 5 5 810 0.2 650 no acceptable back alloy Example 149 brass wristwatch case Co—Nb—Zr 40 40 5 10 5 760 0.15 650 no acceptable alloy Example 150 brass wristwatch band Co—Nb—Zr 40 40 5 5 10 780 0.15 650 no acceptable alloy

[0218] TABLE 9 Decrease in the reception Abrasion sensitivity (dB) resistance Composition of hard Thickness (less 2 kgf Quality of layer (wt %) of hard than −1 dB 30 times of Evaluation external Zr Mo Nb Ta Ti layer (μm) is acceptable) reciprocations result Hardness appearance Example 401 20 80 1 −0.1 ◯ acceptable 1150 surface roughness Example 402 25 75 1 −0.1 ◯ acceptable 950 good Example 403 30 70 1 −0.1 ◯ acceptable 930 good Example 404 40 60 1 −0.1 ◯ acceptable 800 good Example 405 50 50 1 −0.1 ◯ acceptable 730 good Example 406 60 40 1 −0.1 ◯ acceptable 680 good Example 407 70 30 1 −0.1 ◯ acceptable 650 good Example 408 75 25 1 −0.1 ◯ acceptable 550 good Example 409 20 54 26 1 −0.1 ◯ acceptable 1040 surface roughness Example 410 15 70 15 1 −0.1 ◯ acceptable 1100 surface roughness Example 411 20 65 15 1 −0.1 ◯ acceptable 900 good Example 412 25 60 15 1 −0.1 ◯ acceptable 920 good Example 413 45 50 5 1 −0.1 ◯ acceptable 740 good Example 414 40 50 10 1 −0.1 ◯ acceptable 770 good Example 415 50 49 1 1 −0.1 ◯ acceptable 730 good Example 416 50 47 3 1 −0.1 ◯ acceptable 720 good Example 417 55 40 5 1 −0.1 ◯ acceptable 700 good Example 418 50 40 10 1 −0.1 ◯ acceptable 740 good Example 419 40 40 20 1 −0.1 ◯ acceptable 730 good Example 420 50 30 20 1 −0.1 ◯ acceptable 660 good Example 421 70 25 5 1 −0.1 ◯ acceptable 640 good Example 422 50 25 25 1 −0.1 ◯ acceptable 670 good Example 423 75 20 5 1 −0.1 ◯ acceptable 520 good Example 424 20 54 26 1 −0.1 ◯ acceptable 1050 surface roughness Example 425 15 70 15 1 −0.1 ◯ acceptable 1100 surface roughness Example 426 20 65 15 1 −0.1 ◯ acceptable 940 good Example 427 45 50 5 1 −0.1 ◯ acceptable 800 good Example 428 50 49 1 1 −0.1 ◯ acceptable 720 good Example 429 55 40 5 1 −0.1 ◯ acceptable 710 good Example 430 40 40 20 1 −0.1 ◯ acceptable 740 good Example 431 70 25 5 1 −0.1 ◯ acceptable 630 good Example 432 75 20 5 1 −0.1 ◯ acceptable 520 good Example 433 20 54 26 1 −0.1 ◯ acceptable 1040 surface roughness Example 434 15 70 15 1 −0.1 ◯ acceptable 1100 surface roughness Example 435 25 60 15 1 −0.1 ◯ acceptable 920 good Example 436 40 50 10 1 −0.1 ◯ acceptable 750 good Example 437 50 47 3 1 −0.1 ◯ acceptable 710 good Example 438 50 40 10 1 −0.1 ◯ acceptable 790 good Example 439 50 30 20 1 −0.1 ◯ acceptable 650 good Example 440 50 25 25 1 −0.1 ◯ acceptable 630 good Example 441 75 20 5 1 −0.1 ◯ acceptable 520 good

[0219] TABLE 10 Decrease in the reception Abrasion sensitivity (dB) resistance Composition of hard Thickness (less 2 kgf Quality of layer (wt %) of hard than −1 dB 30 times of Evaluation external Zr Mo Nb Ta Ti layer (μm) is acceptable) reciprocations result Hardness appearance Example 442 25 60 10 5 1 −0.1 ◯ acceptable 920 good Example 443 50 40 5 5 1 −0.1 ◯ acceptable 690 good Example 444 45 50 2 3 1 −0.1 ◯ acceptable 800 good Example 445 40 50 5 5 1 −0.1 ◯ acceptable 780 good Example 446 40 50 5 5 1 −0.1 ◯ acceptable 770 good Example 447 40 40 10 10 1 −0.1 ◯ acceptable 750 good Example 448 15 70 5 5 5 1 −0.1 ◯ acceptable 1120 surface roughness Example 449 50 47 1 1 1 1 −0.1 ◯ acceptable 740 good Example 450 40 40 10 5 5 1 −0.1 ◯ acceptable 700 good Example 451 40 40 5 10 5 1 −0.1 ◯ acceptable 680 good Example 452 40 40 5 5 10 1 −0.1 ◯ acceptable 680 good Example 453 80 5 5 5 5 1 −0.1 ◯ acceptable 500 good

[0220] TABLE 11 Decrease in the Abrasion reception resistance Thickness sensitivity (dB) 2 kgf Composition of metal film (wt %) of metal (less than −1 dB 30 times of Evaluation Au Ni P Fe Cr Pt Al film (μm) is acceptable) reciprocations result Hardness C/P ex. 401 100 1 −5.1 ◯ unacceptable 250 C/P ex. 402 8 74 18 1 −2.5 ◯ unacceptable 160 C/P ex. 403 82 18 1 −4.5 ◯ unacceptable 180 C/P ex. 404 100 1 −1.3 ◯ unacceptable 200 C/P ex. 405 92 8 1 −5.2 X unacceptable 500 C/P ex. 406 100 1 −1.5 X unacceptable 200

[0221] TABLE 12 Thickness Decrease in the Abrasion Composition of hard of hard reception resistance layer and metal film layer or sensitivity (dB) 2 kgf Quality of (wt %) metal film (less than −1 dB 30 times of Evaluation external Zr Mo Nb Au Ni (μm) is acceptable) reciprocations result Hardness appearance Example 454 60 40 0.3 −0.1 ◯ acceptable 680 good Example 455 60 40 0.6 −0.1 ◯ acceptable 680 good Example 456 60 40 0.9 −0.1 ◯ acceptable 680 good Example 457 60 40 1.2 −0.1 ◯ acceptable 680 good Example 458 50 40 10 0.3 −0.1 ◯ acceptable 740 good Example 459 50 40 10 0.6 −0.1 ◯ acceptable 740 good Example 460 50 40 10 0.9 −0.1 ◯ acceptable 740 good Example 461 50 40 10 1.2 −0.1 ◯ acceptable 740 good C/P ex. 407 100 0.3 −2.1 X unacceptable 250 good C/P ex. 408 100 0.6 −3.5 ◯ unacceptable 250 good C/P ex. 409 100 0.9 −5.1 ◯ unacceptable 250 good C/P ex. 410 100 1.2 −6.5 ◯ unacceptable 250 good C/P ex. 411 100 0.3 −2.5 X unacceptable 500 good C/P ex. 412 100 0.6 −3.8 ◯ unacceptable 500 good C/P ex. 413 100 0.9 −5.2 ◯ unacceptable 500 good C/P ex. 414 100 1.2 −6.8 ◯ unacceptable 500 good

[0222] TABLE 13 Decrease in the Abrasion Hard layer Protective film reception resistance Composition Film Film sensitivity (dB) 2 kgf Quality of (wt %) thickness thickness (less than −1 dB 30 times of external Evaluation Zr Mo Nb (μm) Material (μm) is acceptable) reciprocations appearance result Example 462 50 40 10 0.1 acryl 25 −0.05 ◯ good acceptable Example 463 50 40 10 0.1 urethane 20 −0.05 ◯ good acceptable Example 464 50 40 10 0.1 silicone 10 −0.05 ◯ good acceptable C/P ex. 415 50 40 10 0.1 acryl 3 −0.05 X good unacceptable C/P ex. 416 50 40 10 0.1 acryl 40 −0.05 ◯ not good unacceptable C/P ex. 417 50 40 10 0.03 urethane 20 −0.02 ◯ not good unacceptable

Industrial Applicability

[0223] According to the invention, a soft metal and a decorative article of wristwatch can be obtained that are high in abrasion resistance, insusceptible to scratches, and excellent in corrosion resistance because of a high hardness of the surface. The soft metal and decorative article of wristwatch according to the invention are excellent in corrosion resistance and thus hardly to cause corrosion, providing a high-class feeling to the decorativeness of the external appearance. Especially when a hard layer to be formed on the surface is in the amorphous phase, the hard layer becomes a smooth film, whereby even if touched with a finger, the surface is insusceptible to a fingerprint left thereon, so that the decorativeness of the external appearance can be further improved to provide a high-class feeling.

[0224] Further, a decorative article of wristwatch formed of an insulating decorative base material with a hard layer formed thereon is not only high in abrasion resistance, insusceptible to scratches, and excellent in corrosion resistance, but also has no influence on the radio wave reception sensitivity of an antenna even when the hard layer is formed thereon, and is therefore suitable for a decorative article of wristwatch for a radio-controlled wristwatch. 

1. A soft metal wherein a hard layer containing zirconium and molybdenum is formed on a surface thereof.
 2. The soft metal according to claim 1, wherein said hard layer contains an additive element constituted of at least one or more elements selected from niobium, tantalum, and titanium.
 3. The soft metal according to claim 1, wherein said hard layer is formed through an intermediate hard layer made of an alloy containing at least one selected from iron, cobalt, and nickel.
 4. The soft metal according to claim 2, wherein said hard layer is formed through an intermediate hard layer made of an alloy containing at least one selected from iron, cobalt, and nickel.
 5. The soft metal according to claim 1, wherein a content of molybdenum constituting said hard layer is about 30 to 75 wt %.
 6. The soft metal according to claim 3, wherein a content of molybdenum constituting said hard layer is about 30 to 75 wt %.
 7. The soft metal according to claim 2, wherein a content of molybdenum constituting said hard layer is about 25 to 65 wt %, and a total content of said additive elements is about 25 wt % or less.
 8. The soft metal according to claim 4, wherein a content of molybdenum constituting said hard layer is about 25 to 65 wt %, and a total content of said additive elements is about 25 wt % or less.
 9. The soft metal according to claim 2, wherein a total content of molybdenum and additive elements constituting said hard layer is about 30 to 80 wt %.
 10. The soft metal according to claim 4, wherein a total content of molybdenum and additive elements constituting said hard layer is about 30 to 80 wt %.
 11. The soft metal according to claim 1, wherein a content of molybdenum constituting said hard layer is about 30 to 60 wt %.
 12. The soft metal according to claim 3, wherein a content of molybdenum constituting said hard layer is about 30 to 60 wt %.
 13. The soft metal according to claim 2, wherein a total content of molybdenum and additive elements constituting said hard layer is about 30 to 55 wt %.
 14. The soft metal according to claim 4, wherein a total content of molybdenum and additive elements constituting said hard layer is about 30 to 55 wt %.
 15. A method of producing a soft metal, comprising steps of: disposing a soft metal and an alloy target containing zirconium and molybdenum inside a vacuum apparatus; evacuating the vacuum apparatus, then introducing an inert gas thereinto, and causing an inert gas plasma to occur; and forming a hard layer made of metals constituting the alloy target on a surface of the soft metal in an inert gas plasma atmosphere in which the inert gas plasma is caused to occur.
 16. A method of producing a soft metal, comprising steps of: disposing a soft metal and a first alloy target containing at least one selected from iron, cobalt, and nickel inside a vacuum apparatus; evacuating the vacuum apparatus, then introducing an inert gas thereinto, and causing an inert gas plasma to occur; forming an intermediate hard layer made of metals constituting the first alloy target on a surface of the soft metal in an inert gas plasma atmosphere in which the inert gas plasma is caused to occur; and subsequently disposing a second alloy target containing zirconium and molybdenum inside the vacuum apparatus, causing an inert gas plasma to occur, and forming a hard layer made of metals constituting the second alloy target on a surface of the intermediate hard layer in an atmosphere of the inert gas plasma.
 17. The method of producing a soft metal according to claim 15, wherein the alloy target contains an additive element constituted of at least one or more elements selected from niobium, tantalum, and titanium.
 18. The method of producing a soft metal according to claim 16, wherein the second alloy target contains an additive element constituted of at least one or more elements selected from niobium, tantalum, and titanium.
 19. A decorative article of wristwatch wherein a hard layer containing zirconium and molybdenum is formed on a surface of a metal decorative base material made of a soft metal.
 20. The decorative article of wristwatch according to claim 19, wherein said hard layer contains an additive element constituted of at least one or more elements selected from niobium, tantalum, and titanium.
 21. The decorative article of wristwatch according to claim 19, wherein said hard layer is formed through an intermediate hard layer made of an alloy containing at least one selected from iron, cobalt, and nickel.
 22. The decorative article of wristwatch according to claim 20, wherein said hard layer is formed through an intermediate hard layer made of an alloy containing at least one selected from iron, cobalt, and nickel.
 23. The decorative article of wristwatch according to claim 19, wherein a content of molybdenum constituting said hard layer is about 30 to 75 wt %.
 24. The decorative article of wristwatch according to claim 21, wherein a content of molybdenum constituting said hard layer is about 30 to 75 wt %.
 25. The decorative article of wristwatch according to claim 20, wherein a content of molybdenum constituting said hard layer is about 25 to 65 wt %, and a total content of said additive elements is about 25 wt % or less.
 26. The decorative article of wristwatch according to claim 22, wherein a content of molybdenum constituting said hard layer is about 25 to 65 wt %, and a total content of said additive elements is about 25 wt % or less.
 27. The decorative article of wristwatch according to claim 20, wherein a total content of molybdenum and additive elements constituting said hard layer is about 30 to 80 wt %.
 28. The decorative article of wristwatch according to claim 22, wherein a total content of molybdenum and additive elements constituting said hard layer is about 30 to 80 wt %.
 29. The decorative article of wristwatch according to claim 19, wherein a content of molybdenum constituting said hard layer is about 30 to 60 wt %.
 30. The decorative article of wristwatch according to claim 21, wherein a content of molybdenum constituting said hard layer is about 30 to 60 wt %.
 31. The decorative article of wristwatch according to claim 20, wherein a total content of molybdenum and additive elements constituting said hard layer is about 30 to 55 wt %.
 32. The decorative article of wristwatch according to claim 22, wherein a total content of molybdenum and additive elements constituting said hard layer is about 30 to 55 wt %.
 33. A decorative article of wristwatch wherein a hard layer containing zirconium and molybdenum is formed on a surface of an insulating decorative base material made of an insulator.
 34. The decorative article of wristwatch according to claim 33, wherein said hard layer contains an additive element composed of at least one or more elements selected from niobium, tantalum, and titanium.
 35. The decorative article of wristwatch according to claim 33, wherein said hard layer is formed through an intermediate layer made of resin.
 36. The decorative article of wristwatch according to claim 34, wherein said hard layer is formed through an intermediate layer made of resin.
 37. The decorative article of wristwatch according to claim 33, wherein a protective film made of a transparent resin is formed on a surface of said hard layer.
 38. The decorative article of wristwatch according to claim 34, wherein a protective film made of a transparent resin is formed on a surface of said hard layer.
 39. The decorative article of wristwatch according to claim 35, wherein a protective film made of a transparent resin is formed on a surface of said hard layer.
 40. The decorative article of wristwatch according to claim 36, wherein a protective film made of a transparent resin is formed on a surface of said hard layer.
 41. The decorative article of wristwatch according to claim 33, wherein a content of molybdenum constituting said hard layer is about 30 to 75 wt %.
 42. The decorative article of wristwatch according to claim 35, wherein a content of molybdenum constituting said hard layer is about 30 to 75 wt %.
 43. The decorative article of wristwatch according to claim 34, wherein a content of molybdenum constituting said hard layer is about 25 to 65 wt %, and a total content of said additive elements is about 25 wt % or less.
 44. The decorative article of wristwatch according to claim 36, wherein a content of molybdenum constituting said hard layer is about 25 to 65 wt %, and a total content of said additive elements is about 25 wt % or less.
 45. The decorative article of wristwatch according to claim 33, wherein a content of molybdenum constituting said hard layer is about 30 to 60 wt %.
 46. The decorative article of wristwatch according to claim 35, wherein a content of molybdenum constituting said hard layer is about 30 to 60 wt %.
 47. The decorative article of wristwatch according to claim 34, wherein a total content of molybdenum and additive elements constituting said hard layer is about 30 to 55 wt %.
 48. The decorative article of wristwatch according to claim 36, wherein a total content of molybdenum and additive elements constituting said hard layer is about 30 to 55 wt %.
 49. The decorative article of wristwatch according to claim 33, wherein said insulating decorative base material is made of resin or ceramics.
 50. The decorative article of wristwatch according to claim 34, wherein said insulating decorative base material is made of resin or ceramics.
 51. The decorative article of wristwatch according to claim 35, wherein said insulating decorative base material is made of resin or ceramics.
 52. The decorative article of wristwatch according to claim 36, wherein said insulating decorative base material is made of resin or ceramics.
 53. The decorative article of wristwatch according to claim 33, wherein said hard layer is a metal film formed by sputtering.
 54. The decorative article of wristwatch according to claim 34, wherein said hard layer is a metal film formed by sputtering.
 55. The decorative article of wristwatch according to claim 35, wherein said hard layer is a metal film formed by sputtering.
 56. The decorative article of wristwatch according to claim 36, wherein said hard layer is a metal film formed by sputtering.
 57. A method of producing a decorative article of wristwatch, comprising steps of: disposing a metal decorative base material made of a soft metal and an alloy target containing zirconium and molybdenum inside a vacuum apparatus; evacuating the vacuum apparatus, then introducing an inert gas thereinto, and causing an inert gas plasma to occur; and forming a hard layer made of metals constituting the alloy target on a surface of the metal decorative base material in an inert gas plasma atmosphere in which the inert gas plasma is caused to occur.
 58. A method of producing a decorative article of wristwatch, comprising steps of: disposing a metal decorative base material made of a soft metal and a first alloy target containing at least one selected from iron, cobalt, and nickel inside a vacuum apparatus; evacuating the vacuum apparatus, then introducing an inert gas thereinto, and causing an inert gas plasma to occur; forming an intermediate hard layer made of metals constituting the first alloy target on a surface of the metal decorative base material in an inert gas plasma atmosphere in which the inert gas plasma is caused to occur; and subsequently disposing a second alloy target containing zirconium and molybdenum inside the vacuum apparatus, causing an inert gas plasma to occur, and forming a hard layer made of metals constituting the second alloy target on a surface of the intermediate hard layer in an atmosphere of the inert gas plasma.
 59. A method of producing a decorative article of wristwatch, comprising the steps of: disposing an insulating decorative base material made of an insulator and an alloy target containing zirconium and molybdenum inside a vacuum apparatus; evacuating the vacuum apparatus, then introducing an inert gas thereinto, and causing an inert gas plasma to occur; and causing atoms of metals constituting the alloy target to adhere to a surface of the insulating decorative base material in an inert gas plasma atmosphere in which the inert gas plasma is caused to occur, to thereby form a hard layer composed of the atoms of the metals on the surface of the insulating decorative base material.
 60. The method of producing a decorative article of wristwatch according to claim 57, wherein the alloy target contains an additive element constituted of at least one or more elements selected from niobium, tantalum, and titanium.
 61. The method of producing a decorative article of wristwatch according to claim 58, wherein the second alloy target contains an additive element constituted of at least one or more elements selected from niobium, tantalum, and titanium.
 62. The method of producing a decorative article of wristwatch according to claim 59, wherein the alloy target contains an additive element constituted of at least one or more elements selected from niobium, tantalum, and titanium. 